Need has nothing to do with it. want has EVERYTHING to do with it. If you don't already have a 7x57 then you really do need it and if you do have one it never hurts to have a spare.
I have 3 1893 Mausers in 7x57 and an 1895 Chilean Mauser in 7x57 but none of them are actually hunting rifles. I'd have to arrange and out of State hunt to use it. But, you are right, need has nothing to do with it.
kwg