Retail faces many of the same problems - you can check the quality of a pair socks, but if you order a million of them there can be high quality variance and detecting that is non-trivial.
Also common is that you check and verify the quality of socks but 2 years down the line your vendor starts screwing you with lower-quality equivalents.
Quality control is a hard problem in any field.
> "But what stops the place from dropping standards as soon as they get curated? Monthly surprise reviews?"
That's what we do for restaurant hygiene - and at least around here it seems to keep a reasonably good lid on things. With the help of software it's also relatively easy to identify patterns of failure (as opposed to irregular lapses in quality).
> "Even hotels are spotty"
They can be, and this is a large part of why hotel chains even exist - they exist because quality information is really spotty and so the chain is essentially a guarantee of some consistent quality expectation.
Yeah, part of the problem is that many of these companies are middlemen and almost completely uninvolved in the actual product being sold (see: Uber doesn't manage any of its own cars, AirBnb doesn't manage any of its own rooms), and so far the pattern has been to pass the buck to customers with a "buyer beware" notice.
I contend this is not good enough - especially when many of these services are high-priced and advertised as substitutes for actually-curated (see: hotels) products with solid quality assurance. IMO in many of these cases companies need to do more for the margins they charge (e.g., Seamless charges 15% of all orders, but they don't provide any portion of the service, not even the delivery bits unlike Caviar or Postmates).