At least for majors…I would think that having your coach on your bag would be a huge advantage to quickly fix swing issues. You’d probably have to pay them more than your regular caddie, but it would probably be worth it.
Most golfers share coaches, so it wouldn’t be possible for every golfer to be accompanied by a coach.
Lugging a pro golfer’s bag through 18 holes of resort course is backbreaking labor. I’ve done it. Most of the top coaches are not going to be interested in this line of work.
During the round is not a good time to fix a swing. "Keep your head down"and “keep your left arm straight” are about the most effective coaching you can get during a tournament round. There is not time to fix a swing flaw, and working on it will likely just screw you up. That kind of work is better left for the range.
I think it’s because most coaches haven’t gone to caddy school. That, and caddies aren’t only expect to know their player, but they’re also expected to know the course in intimate detail. Most caddies fly out to a tourney days before the first round starts, and they play the course multiple times, and walk off yardages to hazards, hills, trees, etc.
Coaches are doing what they do as a stable profession. There are thousands of professional golf instuctors in the United States, but I’d venture a guess that a single-digit percentage of them have a student that’s making a living on the tour. And if you’re looping for a pro, if they ain’t winning, you ain’t making much money.
I understand the conflict of interest issues that would arise for a coach with multiple players in a tournament. I wonder if there’s any rule, written or unwritten, preventing such a scenario.
Try to picture 90 year old Harvey Penick carrying Ben Crenshaw or Tom Kite’s clubs around in the heat for 18 holes…
Not pretty, is it?
Hey, if it helps me win a major, I might just decide to carry my own bag and let him instruct me as we go. For one thing, pro golf bags are filled with tons of unnecessary junk. I’ve played plenty of golf where I’ve carried my own bag.
Coaches charge hourly, while caddies work contingent! 
Coach = Caddie.
Seriously. Asking this question is like asking when a baseball team doesn’t have it’s pitching coach as it’s manager since he’d be able to make the pitching changes better.
A Swing Coach is one type of coach. A Caddie is a different type of coach with a different set of responsibilities. One fixes a guy’s swing, another studies the course and provides a second set of eyes. Why you’d want to sacrifice course knowledge for swing knowledge is baffling, which do you think would be used more often while playing a course?
I guess that is one way of looking at it. I tend to think moreso that swing, shortgame, etc "coaches are more akin to “instructors”, whereas caddy is more like a personal assistant. But you are certainly correct to the extent that they perform different, and equally useful, functions.
That might be true for regular tournaments but for the majors, a lot of players hire course specific caddies. For example, a lot of players have caddies that double as their assistant (make reservations, drive them around town, does the scheduling, etc.), they know the game generally and they know how you play. But, if a game is important, they hire a course specific caddy that knows stuff about a course that you can only know if you play (or caddy) the course regularly.
On the PGA Tour, this is not that true. Most of the regular Tour players use their regular caddies in the majors as well as the regular tournaments. VERY occasionally, someone will hire a caddy at the Masters who is an old-timer for Augusta National, where local experience is a good thing.
It probably depends on the golfer. Steve Williams, Tiger’s caddy, is a full time employee and travels with him everywhere. His first job is to learn the courses and know the nuances. His second job is to be his sounding board and help keep him on regiment. This scenario is common with the most elite of golfers, but rare in general.
The best golfers have full time guys for every event, but probably the majority hire caddies specific to the course. I highly doubt many caddies are doing personal assistant type duties like booking rooms and the like. Mid-level golfers probably have personal assistants (or wives) who handle all their business and travel needs and a sports agent to handle appearances and money but I doubt many double as caddies since the job is just too important.
I think that many of you may be over-estimating the role of the caddie. Certainly, some caddies are basically coaches. But not always. Many pros will just use a close family member as caddie. In the US Open, the 2nd and 3rd round leader was using his brother as caddie. He would have been much better served using his coach. Most caddies are NOT analogous to a hitting coach or pitching coach. Even Nicklaus often used his kids or grandkids as caddies, although not when he was in his prime. I’ve seen other players use their daughters and sons as well.
It’s VERY rare that anyone in actual contention would use a amateur like a family member as a caddie. I’m sure it’s a lot of fun for the golfer, but those guys have already resigned themselves to the fact that they aren’t in it to win. Even still, it’s almost always golfers who have a ton of experience on a given course who would make such a move. Older guys or hometown guys. In those cases their knowledge of the course would probably be equal or better than a caddies anyways.
ETA: I have no doubt that there are a lot of golfers who’s personalities simply don’t allow them to use caddies effectively. Some people, especially in a solitary sport like golf, simply need to be their own council on all matters and just don’t accept guidance or advice. For a player like that a caddie might be nothing more than a bag boy. However I’d wager that those guys don’t win many tourneys.
I may be mistaken, but ISTR hearing that Veej pretty much wanted his caddy to provide him yardages, hand him the requested club, clean his ball, and little else.
Also, didn’t Stricker’s wife caddy for him for several years?
As other have mentioned, Coaches have multiple clients. If a coach is caddieing for Player X, the coach is of no use to Player Y when Player Y is warming up for his round.
As others have mentioned, Caddying is very time consuming. If I was a pro, I would want the caddie to surveying the entire golf course, not coaching one of my competitors.
Someone mentioned the 2nd and 3rd round leader at the US Open. (Ricky Barnes) Ricky had his older brother on the bag. Barnes was clearly not comfortable in his position and started to lose his game. As an older brother, I would have been his face to get his head out of his ass, get back to his fundamentals and telling Barnes that he was still going to win the US Open.
A caddie is a confidant, a sounding board, and most of all should be amateur sports psychologist.
Non-golfer with what should be for you an easy question. I understand the pros can’t use carts and the bag must be carried. Are bags with wheels allowed?
Pull carts are allowed, even motorized ones. The rule against riding in golf carts is because the walk is considered part of the game.