It is always fun to use different machines. Just like personalities, each machine has a different one. I have 4 or 5 featherweight machines, I can't remember how many since I gave one of them to a friend. Each of those machines sews differently, the same, but different. I have a Janome 6600 and a Bernina 1030??. The Janome has an automatic walking foot and is wonderful to use. The Bernina, I have had forever and it is just a great work horse.
You are right, who needs that many sewing machines? However, it is always great to have a spare when one of your machines breaks down. Different machines work better on different projects. As for the featherweights, I just kept finding them selling at ridiculous prices, and who can pass up a great deal for a featherweight? I know I can't.