He, “works alone,” as in not with a minor subordinate sidekick. Even with full adult Supers who have powers of their own he is not shown as being a team player. Professionally, Elastigirl and Mr. Incredible were competitors in the same field. He didn’t work well with either her or Frozone back in the old days, though they were obviously friends outside of work. It wasn’t until the end of the movie — when he’d had 15 years of domestic partnership and life as a “normal” to train him, and had recently had humbling and probably life-changing experience — that he cooperated effectively with others.
Besides which, he explicitly tells Buddy that what he does is dangerous. He thinks hero work is not suitable for a child, especially one without protective innate abilities, and most especially a minor who is volunteering himself for hero work without the consent of his parents. In the scene with Bomb Voyage, Buddy nearly gets himself killed, and he would have died if it wasn’t for Mr. Incredible.
Granted, Mr. Incredible could have been more tactful in how he rejected Buddy, but let’s face it, the kid had been harrassing him for who knows how long, had interfered with the apprehension of a criminal, and had put himself and, indirectly, other people in considerable danger. He had already told Buddy on multiple other occasions that he wasn’t interested in having a sidekick. I think I would have lost my damn patience with Buddy too, and I’m a lot less volatile than Mr. Incredible is shown to be.
Given the world the writers set up, which is remarkably internally consistent for a movie of this type, no the Supers couldn’t have worked in fields that let them use their abilities. The whole reason for secret identities is to give them some security when they’re not working. No one, not even Superman, could be on all the time. Anything that had the possibility of “outing” them would have to be avoided. They or their families (who are not necessarily Supers; the Parrs appear to be an exception here) would be in danger if anyone knew who they were. It’s hinted that they would have faced persecution from normals, and they had certainly made a lot of enemies, both Super and non-Super villains.
That means anything that could expose Bob’s exceptional strength and toughness would be out. No furniture moving, no sports, nothing physical. Two scenes cut from the movie for time and flow reasons were: 1) Buddy as Syndrome invading the Parr’s house in the middle of the night and kidnapping Jack-Jack. That kicked off the story in the earlier version of the script. There would probably be dozens of villains like him trying to attack their family if Bob or Helen’s real identities were revealed. 2) Bob not paying enough attention to what he was doing and “cutting” his fingers with a knife at a barbeque. Helen and he have to leave suddenly, covering up the fact that the knife blade was damaged while Bob wasn’t hurt at all. Their nervousness shows that little slips like that could be very damaging.
Something else I just remembered from the movie was that they all still have lawsuits that could be brought against them. As part of the amnesty they were to go into hiding and not use their powers. Every time Bob screws up, the government has settled these new suits out of court and paid money to move his family. But if their protection were removed, he would probably be financially ruined, even if he had no new suits brought against him.
I get that you and a few other people don’t like the movie, but I think that you’re looking at it from an extremely biased point of view. As I pointed out earlier, super-powers are not be significantly different from other gifts. It is manifestly unfair to say that one group of people should not use their abilities. It sets a double standard, where the exceptional are obliged to hobble themselves so that they don’t outshine those who are less adept. I find that attitude pretty darn distasteful, myself.