I think review inflation is a problem in general across any service where there might be a more human/personal interaction element where you might feel compelled to be nicer or more generous. It's very different than buying a product from a retailer or rating a product from a company you've never had a direct personal interaction with. I think for most of us, it's in our human nature to be more generous unless there's an egregious violation of standards/quality.

I think it depends on what the bad experience has cost you, and about the dynamics about the particular platform/system.

If I have a bad Lyft ride, I usually won't rate any lower than 4 stars, because of exactly what you're talking about, and because I know that an average rating of below something in the mid-4s can get a driver "fired". The ride may have been sub-par, but its purpose (getting me from A to B) has been fulfilled, and that's that. It's also probably on the order of single- or low-double-digit dollars, so I didn't spend too much on the bad experience. And again, the actual purpose of spending that money has been fulfilled. (Now, if a driver is actually driving unsafely, they get 1 star, plus an email to Lyft customer service, no matter what.)

If I've planned a vacation, however, and the Airbnb ended up being a bad experience, I'm absolutely going to write a bad review. I've likely spent a decent chunk of change on it, and I'm specifically spending that money (plus the money spent for transportation to get to this place) to have a good time. If the accommodations aren't as promised, and it impacts my ability to have a good time, then I'll leave an honest negative review because I haven't gotten the value I expected for that money.

I rented a place in Tahoe for New Years this year that ended up having some significant negatives. My friends and I still had a good time overall, but having to deal with the issues was frustrating and definitely detracted from our fun. It wasn't through Airbnb, so I left a detailed negative review of the management company on Yelp. I didn't feel bad about this; the people from the company I interacted with were friendly and attempted to be helpful (but fell a bit short in execution), but the cleanliness and condition of the property was below what I expected, so... bad review.