because: 1. lvls and tiles made with 1.23 work with both 1.23 and 1.24, while 1.24 can only be hosted by 1.24
also, 1.23 is less "n00b". Most new players turn up on 1.24 (Europeans), because TSF is widely distributed in Europe, and is cheap (plus you dont need to get patches, which you do when you buy a non-TSF version)
A new character is good, is fun, but one that cant hang onto a chopper and has weird looking colors..nofun.