I think this is due to:
1. Valve's fascist STEAM protocol and micromanagement. If you mod on the Source engine, you have Valve breathing down your neck.
2. The majority of dedicated Valve fans are of the Counterstrike variety. They don't really have any intention to try other types of gameplay, and certainly not a pay MMORPG, they just want more free Counterstrike or "bonus content."
3. It's extremely time-consuming to make anything but a simple multiplayer mod. It's also difficult to make anything complex with an inexperienced team. It's not impossible, but you have to be realistic with your options and capabilities.
And I think that you're just fucking stupid.
1) Source Engine games don't have anything innately to do with Steam. You don't have to use Steam and many licensees won't. Furthermore, just because a game doesn't use Source doesn't mean it won't use Steam -- look at the non-Source Steam games like Red Orchestra. Also, modding a non-Steam Source game like Vampire won't have anyone breathing down your neck. It's your problem that you're too goddamn stupid to seperate Half-Life 2 from the engine it uses.
2) You don't have to be a Valve fan to enjoy a Source game. Do you have to be an Epic fan to enjoy Unreal Engine games, like Splinter Cell, Lineage 2, or Deus Ex? That's one of the most ignorant fucking conclusions ever made.
3) This wasn't a mod, smart guy.