I used to make these types of games all the time when I was younger, and they're still pretty popular. I guess it all started with A3 http://alienaa.com and some space trading game I forget the name of. They were probably just a natural evolution of BBS games. Making text-based browser games was why I even started programming to begin with when I was 14 or 15, and for a while there were a bunch of games derived from code that I wrote and handed out long before I really knew how to do open source. Seems stupid of me now to have never thought of trying to make money off of them.