I can be seen as a craft-a-holic, with two characters, one being a 16 Cleric/23 Sage, and the other being a 7 Scout/ 24 Alchemist, and I tell you, once I got the starting money up to start crafting adept 3s, I can make about 25 to 50gp a day, sometime more. That in itself is a pretty good motive for many, but...the real reason why I chose to craft instead of adventure, is just because I like it more, and have more fun doing that instead of adveturing. I think adveturing is ok, but to me, crafting is more rewarding, and I also enjoy the thank yous from other players when I give them a good price on a rare item =)
I find that crafting acually has more depth than adveturing, once you begin to realize that every combination of tradeskills pushed at each table has a different effect, when you start cratfing rares, working out deals for dependency items, the deals you work out (I realize that the last 2 are player interaction, and not actually coded game, but it is still depth) etc