Bit late to the party on this one, but I wholeheartedly agree with Jack and Tootler.

It's not about 'The Recorder Police' or any such straw man - it's because that's the way it's been done for literally hundreds of years, and by failing to take the plunge the OP's friend is only storing up a problem for the future for the reasons that other people have already explained.

It'll only take a few weeks to get used to reading F parts, and then it's a skill that is learned for life.

I play every size from garklein to bass and find switching between the F and C notations very straightforward, and furthermore find that the experience / concept is very useful in other musical ways as well (particularly, in my case, writing saxophone parts).