Why not startup => company => provides services and products => exit?

Well one reason would be that the startup needs to be bought by someone in the right position to exploit it before it can become profitable.

So in that case, you could create a startup that in itself cannot be profitable, but when purchased by a larger company can become wildly profitable for them.

I don't think that's an unusual case.

haha which is why all companies were startups at some point but not all startups will be companies.