I've got 12 machines (I think), but I didn't buy them all. I inherited some of them from my grandmother and great-grandmother.
1. Singer that my parents bought me back in the late 70's or early 80's - no longer works
2. Singer that I bought myself in the late 80's or early 90's - still works for the most part
3. Juki on a queen-size frame for quilting - bought 2 or 3 years ago
4. Serger - bought 9 or 10 years ago
5. Singer Featherweight - bought because it's cute (LOL!)
6. Brother machine - bought a couple of years ago to replace #2 above
7. Brother embroidery machine - bought a couple of years ago for embroidery only
8. Singer 15-91 that I inherited from my GGM (missing parts)
9. Singer 15-91 - bought off eBay - works like a dream
10. Pfaff 7570 - inherited from my GM - nice machine, works great, but it seems "weird" to me (not as user-friendly as my others?)
11. Another Pfaff - inherited from my GM - haven't used it at all
12. Another Serger - inherited from my GM - haven't used it at all
As far as why I bought the ones I did, I like to have backups for my regular machines, and some are for specific purposes (quilting, embroidery, serging, basic sewing, etc.).