Yes, there are definitely pretentious shops that just don't want to deal with department store bikes in general, for sure.
But...
There are also a crap ton of people that come in with huge problems like "It's loose when I pedal" or "The back wheel is all wobbly." When you tell them "Your bottom bracket is broken and needs to be replaced, which will be anywhere from $40 to $60 in parts and labor," or "Your rear hub is loose, and it's at least $10 to get that wheel off and tightened, and that's if the bearings in the hub aren't broken," then they cuss YOU out. "Man, eff that. You MFers expect me to pay another $60? I barely bought it a couple months ago for $75."
It's... frustrating. I've told customers before "I don't expect you to do anything. I'm just telling you what the problem is and what it's going to cost." And then it turns into a back and forth that goes nowhere and is just a frustrating waste of time. "I thought it would be like $5 to fix it. I can't do $60 for a bottom... whatever you said. Can you all just tighten it for like $5?" Of course not. It's... broken... internally. It was made with crap parts so you could buy it for $75 and think you're getting a steal.