I think you must mean that covered calls or the wheel are less lucrative than more complex strategies, unless I'm really missing something. Can't get much simpler than a CC.
The Wheel as a strategy doesn't scale well, though. A good stock for the wheel has relatively low volatility, but with high volume of option interest. These two things are kind of opposed to each other, though. If a stock isn't very volatile, then there isn't much need for large option interest.
Of course there is a lot of overlap where things get interesting.
I think the reason why there aren't a lot of institutions running the wheel et. large. is because it just can't work at the scale they want to operate on. You can probably run the wheel pretty successfully at a million in capital (much larger than I'm used to), but at 10, 100, or 1 billion, it just doesn't work.
And what are they going to do? Pay some guy 200K to generate maybe 200K on a million in capital?