I generally have more than one reason for doing any given thing.
Reason 1: I had a lot of 1:72 armies left unpainted from when I was a kid, and decided to finish them, to use for HOTT, though I quickly converted them to DBA armies. One thing led to another and I just kept building.
Reason 2: 1:72 is a good compromise between 28-30mm, which allows fantastic detail but requires a house-sized space to game in, and smaller scales I would struggle to see.
Reason 3: 1:72 sets are pretty cheap.
Reason 4: 1:72 minis are very durable, and I am clumsy. I know that every so often I am going to drop an element from a shelf that is up to 6' off the floor and all the minis will be intact when I pick it up.