I got a couple of anecdotes about that very same thing.
Whenever I read very, very expansive plots and stories in a thread, I feel like I am reading a story that has already been done rather than one that is waiting to be made. And before I decided to not engage in those kind of RP-premises, I found that those players pitching that were the most incessantly demanding people on how the RP should turn out. I can absolutely understand that when two people discuss an idea and create a premise and a story that both people shouldn't throw in some curve balls, but it was to the point of being pedantic and obsessive most of the time.
So here I am, going for character-based pairings more than intricate storylines and do not write very, very complicated and strictly outline backgrounds for my RP's :')
And on a side-note, whenever I GM; I insist that players realize they are playing as characters beginning their adventures that will grow into heroes, not heroes starting out. Makes things more interesting, but bla bla bla, helps people playing characters that grow into their role and personality.
This guy has a good video on it.
Anyway, back on topic.
It's easy with a kind of anonymity to disengage from potentially awkward conversations that might lead to nothing, than just dropping an RP that they
perceive as being a lost cause. But sometimes people don't reply for a long time, then feel silly or guilty picking it up after a long hiatus and just don't touch it out of fear of
annoying someone that they
insulted by dropping an RP they had with in the past.