Yeah, they don’t want it solved.
The Rich family is either incredibly-stupid, paid off or threatened. Or some combination above.
My personal theory. Seth Rich’s parents are not Mensa. They have been persuaded that believing anything remotely connected to a ‘conspiracy,’ would make them look stupid, and have their neighbors laughing at them. They believed it. So even though they are basically honest and loved Seth vastly, they are afraid to question the official narrative.
Jmo.