If all you do is quilt, you don't need many feet. If you do general garment sewing, heirloom sewing, or lots of home dec work, more feet are handy tools. I look at a foot as a tool to help me do something faster. I could do everything with a zigzag foot, but applying piping or doing pin tucks or doing a blind hem is an awful lot easier with a good foot!
Bernina feet are expensive but they are high quality. I am still regularly using some I bought 20 plus years ago. Of course, it is probably obvious that I do a lot of different types of sewing!
Pam