I sometimes wonder why I have so many myself, but...My main machine is an Elna Quilt Queen Pro (love it), a Singer H74 for a travel machine (computerized by not extremely expensive); my Mom's inexpensive,lightweight Singer (don't know model) that isn't computerized and I've saved so that the g-kids can use(her ancient, heavy Kenmore with cams for different stitches went to my son); I also have a treadle (Singer) just cause it reminds me of my Mom sewing in the bathroom (only place with space!) on one when I was little, I also have an industrial ConSew heavy duty machine that rarely gets used but it sure is nice for upholstery, etc. I also have my 2nd machine, a very heavy Deluxe that is all mechanical, and then the Gammill long arm.
I think most of us that have more than one machine either have several because of different uses or just because we like the machines!