The appeal of SFM (Source filmmaker)

One of the reasons I  got into blender was because of artists that use Sfm (Source filmmaker a game engine that is owned and created by the Valve Corporation) for their animation and art pieces they make in their free time.
years ago I tried to learn the program but due to how old the program was and the lack of care put into maintaining it by the company it didn't seem worth pursuing someone told me to try to learn blender instead after using blender for 2 plus years one thing I don't understand is that a lot of really skilled animators still rather use SFM a very dated program and having to use a mountain of hacks/ tricks, to get the results they want when they can use blender or Unreal engine and have less hassle I've asked around to people in the SFM community and I have yet to get a straight answer. so my question is. Why use a program a company doesn't care about even when their fan base is enormous. when you can use a program that can do pretty much the same thing and more also with an active development team seems kinda strange to me. What's the appeal of the program?

is it because it's is easier? what makes people stick to the dated software. is there something the blender Devs can learn from SFM to implement in their own program? if you are an sfm user or just want to share your own thoughts on this matter please feel free too.

 I'd really like to know.

Share your thoughts. :)

If you don't understand what I'm talking about I'd say go take a look at some of the animation made with SFM it's crazy what people make and rather stick with that program than switch.