They are right there in the same league - playing the same sport as the saying goes. Very small air-ends driven "hot" at high RPM and made of very cheap materials. The goal is cost savings and the market is flooded with lots of competition. They build the machines as small as possible and rate them at CFM they can only achieve by running at 1800 or sometimes 3600 RPM! A proper compressor that's going to live a long, happy life needs lots of cast iron, large oil capacity, pressure fed lubrication, proper oil and air filtration and MOST OF ALL it needs to run at a healthy 900 RPM max. Even at that RPM you can easily hit discharge temps of 350 *F when running continuously for 30+ minutes. These tiny big-box-store machines would die a horrible death if run continuously for 8 hours at pressure. Which - coincidentally is the BREAK IN run for new rings on a Quincy QR series. We operate them for a full 8 hour work day at 100 psi. They can do this for DECADES and they love doing it.
Both HF and Sears/HD use entirely Chinese components. Some of the higher end units may have bits in their build from Taiwan... but by and large none of these machines would hit 1,000 hours of operation without a 99% failure rate. The fact that many live on for years of abuse in the hands of people that use them once a month to inflate a bicycle tire is pretty much meaningless data. I could show you dozens that lasted a week or less on a real job site.
I get it - real compressors are expensive. But that's what craigslist and the used market are good for. Lots and lots of machines out there that need a good home and some TLC. I recently picked up a QR-240 at a sale for $100 - it was laying on it's side in some brambles. Turned out to be a WW-II vintage machine of US Navy origins. I did a service on it and put in new rings and bearings and it's running great. Total cost was probably in the $300 range. It's a 5 HP single stage machine that makes 17 CFM all day long at 120 psi. It runs at a tollerable 850 RPM and you can talk to someone standing right next to it.
GD