As a player. No reason. But dors not matter a lot.
As a 3pp, you need to decide: use the new OGL and profit from using D&D or doing other things that might be way less profitable.
In a different thread a 3pp said, that one of their books was sold 20 times as often with 5e as the same book with alternate rules.
I also do a guess and say LevelUp sold more often than WOIN.
So the question is: are the new conditions good enough to use or not.
I understood Morrus, that he wants OGL 1.0 or nothing, and I think he might be in a good position. Big publishers also should be able to do their own thing.
I don't think every small publisher will be in an equally good position.