That's what's so nice about sewing machines. There are plenty of niches for collecting them. Some may want to focus only on Singer model 12s for instance. Others may want an assortment of Japanese zigzag machines from the 50s and 60s. Others may want only early machines from before 1900.
I'm fascinated with the early development of machines from treadle to electric. There were a bunch of different ways to hang a motor on a machine. Some of the early conversions and electrified machines are fascinating to me.
Rodney