To me this sounds like complaining that PCs can say they're going to the general store, knock off some coins and just add the equipment to their sheet without RPing locating the best shop and spending half a session haggling with the shop keeper. Some groups will want to gloss over it, some will want to RP it.
"Complaining" probably isn't the best word.
Most groups IME do not role-play PCs shopping for equipment. I would find it very tedious if a DM insisted on role-playing such mundane tasks and encounters in general. Occasionally it is done, but that is because the purpose is
really to introduce an NPC, adventure hook, or similar.
I choose to see these as an opportunity to start a roleplay scene. Characters get a hint on where to start. The criminal PC knows where to go to find the local fence, maybe ask a few questions and get some illicit/cheap gear. It gives the DM a chance to introduce an underworld NPC who may have a job or two for the PC in addition or in return for the information. Same thing with the noble - the character gets a foot in the door into the political machinations of the area they're traveling in, trading favors and information for missions or possible intrigue or even introducing a returning NPC.
Sure, but all of these revolve around starting an adventure or during its process, not mundane situations.
Using the Criminal example. The PC already "knows somebody" and likely where they might be. Which is fine, but it means the rest of the group never has to try to find the fence, deal with other underworld elements in the process, etc. That "part" of the challenge, or scenario, is already done automatically by the PC background feature.
Generally, such things aren't
huge issues, but sometimes they just take that extra little bit out of the equation, making it in essence (if not in reality) obsolete.
If the DM wants to skip over the interactions, or feels it doesn't apply, that's always their call. But I'd like to leave them in for the opportunity to give the players an avenue for mechanical benefits based on their backstory - to give them a springboard for abilities that aren't combat-centric.
Certainly, and depending on the current situtation in the game, sometimes they get glossed over, other times maybe only handled minimally, and yet other times are handled completely in game. It just depends.