Because not everyone is of the opinion that SC2.0 is a "better" game. I, for one, don't see the need to unlearn D20Modern to learn a new, very different, system that doesn't improve a whole lot. I know and work with d20Modern already, and I know how to get it to do everything I want it to do ... and if I find something about another system I like better, I know how to add that to Modern as well.
Not that SC2.0 is a BAD game. There's just a boat load of changes in it, and not all of them I feel need to be made to play a fun game. I liked the different way to do NPCs, especially self-scaling NPCs, so I brought that over to the system I already know. I didn't like, say, shifting Initiative counts or the skill system in SC2, so I didn't bring that over. I don't like WP/VP, how SC2 handles firearms, how it handles multiple damage types, any of the classes, how it handles wealth and gear, etc etc.
I liked the NPCs, the Dramatic Conflicts, and Stress Damage.

I'm working the kinks out of Stress Damage. I tried using it in a d20 Dark*Matter game, but the slower pace didn't work with the Rules As Written in SC2 (which is written for action spy genre games) ... Stress never built up in the few games we tried it in and it ended up being "yet more dice, yet more numbers" with no pay-off in tone or atmosphere ... so I'm reworking it.
--fje