Clearly only 'certainly shady people' use onion services, for example intelligence services, government agencies, technology enthusiasts, drug dealers, software engineers, yakuza, and 8th graders.
I think it doesn't matter if they are shady or not.
As long as a way of transferring goods and payments can be agreed on I guess most thieves wouldn't care who their customers are?
They definitely care if their customer are cops, though.
Not necessarily: My point is as long as the handover can happen in a "safe" way and they are sure they haven't left any prints, dna or other traces, why should they care?