Boot drive full; Backups of 3 iPhones 3 iPads. Can't apple modify future iTunes to save backups elsewhere?

My laptop's boot drive is almost full only due to the fact that I have backups of 3 iPhones and 3 iPads on it. I have deleted all the duplicate or older backups for each device but still have not been able to free a lot of memory.

Why can't Apple modify iTunes in future updates that would permit us to save back ups on a drive of our own choice?