>I wonder why it is so hard.
If you are actually curious, it's because of a mix of reasons: ongoing software developments that could broke such feature in the future if we were to do it now even if it's simple, small number of devs (who would get burnt out if they work), and hardness of hiring PHP devs who would work on this software we are using with reasonable prices.
I did note your suggestion to see if it will be an easy thing to implement later, though. I appreciate your interest

I was asking more for kinds of ideas that wouldn't require anything on software level. Someone in the past privately suggested occasionally holding contests for example, that's doable in a non-competitive level. This is just my opinion, but I think /kaki/ should be a relaxed place for artists of all levels to have fun drawing, let it be serious artworks or humorous sketches - hence it exists alongside with /art/ board.