(As another anecdote, I once tried to get a photo from an iPhone onto a Linux PC without having to sign up for some cloud account first. After about an hour of fiddling, I ended up e-mailing the image to myself.)
This isn't necessarily true. You might be able to get a better grip on a bigger phone - if your hands are large enough. Personally these large screened phones (and I have the smaller of the two iPhone models) are too large for me. If I put a case on it actually makes it more difficult and impossible to use one handed. If they were to make it slightly thinner (I don't know how possible it is at this stage) it would be easier for me to hold as the difference between case/no case, despite being only a few millimetres is actually pretty significant.
Oh, and it has a headphone jack, too.
But it was nice for manufacturers to toghether maintain this artificial problem.
Say "Think different", but give everybody the same product, that is how things work at Apple.