As opposed to a solid foot with the toe bones internal. Sort of like a flipper.
I suppose it could make for more flexibility when climbing or perhaps even walking. The flip side (ISTM) is that it makes for fragile toes, which are more likely to break.
In any event, as a practical matter, I would think today when people rarely climb or even walk barefoot on uneven surfaces, that people might be better off if they did not have individual toes.
Any Advantage for Humans in Having Split Toes?
I use them for picking up bath towels and shoes.
Flip-flops
For humans, who don’t have opposable big toes (like chimps, gorilla, orangutans, etc.), I suspect independent toes aren’t particularly an advantage so much as they are not enough of a disadvantage to matter when it comes to survival of the fittest (more like survival of “that’ll do”). I think they’re inherited from whatever ancestor of ours had opposable big toes, which lent hand-like dexterity to their feet.
Was amused once to see a video of two baboons mating, and the male was using his opposable-big-toed feet to climb up (and grip) the female’s hind legs. That would come in handy now and then…
I grip with my toes when walking on rocks.
I had a friend who had two of his middle toes fused on both feet as a birth defect. Didn’t seem to bother him much.
If it was that much better more animals would have fused flexible toes. A dolphin uses flippers mainly to steer and propel in the water, quite a bit different from the weight bearing load on toes which have to perform propel and steer on land, not to mention climbing and picking up small objects when your back is as old as mine is. Also, one broken toe doesn’t put us out of action because we can largely compensate by keeping the load off it. If you only one big wide toe you might be out of action from any injury. Finally, there’s something some people do in bed which would be much more difficult with your scheme.
Sure, but does it matter that the toes can move independently, or would your grip be OK if your toes were all webbed to form a flipper and had to move together?
Ever do any rock climbing?
And pens and pencils.
Really creeps out my office mates 
There are a lot of things we’d be “better off with”, but evolution doesn’t work that way. Not sure you’re implying that, but just in case. Obviously, though, our toes have shrunk considerably over time, and maybe they’ve found the right balance (ha!) between being an impediment for walking and not mattering any more. It’s also imaginable that our recent ancestors used toes to hold hides while scraping them or string, yarn whatever when making garments or any such other use that helps free up the hands for the delicate work.
Think about it: Humans, walking upright, are relatively tall and thin with a very narrow base and high center of gravity. It’s a real trick that you humans are able to stand upright on your hind legs and balance and walk easily. This is right up there with flamingos sleeping on one foot.
I’m pretty sure the separate toes have a lot to do with that.
Try this experiment: Stand on one foot (preferably with shoes off). Try to get yourself reasonably stable. Now, pay attention to something you probably don’t pay much attention to: What are your toes doing while you’re standing on one foot?
You’ll notice that your toes are continually shifting your weight around from toe to toe. It’s like playing a piano with your toes. You do this entirely autonomically, and never even notice until you make it a point to notice.
Without them, you couldn’t wear Toe Socks! 
Unlikely.
My toes don’t move.
Even species with solid limbs still have 5 separate bone groups corresponding to five digits.
http://scienceline.ucsb.edu/getkey.php?key=3067
http://www.realclearscience.com/blog/2013/09/toes-are-disgusting-do-we-need-them.html
Do it with your eyes closed.
This. Ultimately, humans evolved from ancestors with separate toes. The was no evolutionary advantage in them being fused (as it is for a dolphin), and no disadvantage in keeping the as they were, so they didn’t fuse.
I’ll point out that split toes provide more traction in loose material when running after prey or away from predators barefoot as our ancestors were doing as we evolved.
I’m thinking about toenails in this regard.
We certainly don’t need them now. They just get dirty, infected, broken, etc.
But they must have been quite useful to our ancestors not that long ago (1-3 million years back).
And 5 toenails on a fin foot would probably not be at all useful. So until we evolve away the nails, the toes are going to remain the same.
