I see what you are saying, @Indigobeetle!
I think a part of it is that a fair share of jammers are still making some of their first few games and probably just haven't developed the skills to think about implementing a wide array of games quite yet.
I also think the theme "Overload" is more flexible than previous ones (like Ascension, Malfunction, Train, Rain or Shine, etc.). I believe this is the primary cause. Sometimes, I like to be really "on" theme, but also avoid anything that I think would be commonly implemented ideas.
I'd like to think that I'm in a similar boat as you--sometimes I'll care TOO much about the theme instead of making something fun. For this jam, I really wanted the game's main crux to be struggling with Sensory/Information Overload.