Would say that some things are evident before the viewing eg no parking, or separate dining room yet viewers till go and see the house then reject it on that basis such a waste of time
Thing is though, although you might know there is limited parking, if the house were perfect in every other way, then that might matter less to you as a prospective buyer. Because, having viewed the house, you found it to be "okay", then the limited parking carries more weight. I suspect almost everyone has to compromise over something when buying a house, but the 'pluses' have to be bigger than the 'negatives'.
As a pp said, sometimes you don't really know what you want, until you see it. Just as when we bought the home we've lived happily in for the last 15 years - it wasn't really on our 'wanted list'. We agreed to look at it (suggested by the agents) along with 2 others we chose ourselves, all on the same day This one was a bit out of our price range and a bit outside where we'd been looking, but the moment we walked in we knew it was 'the one'. When we are selling, we have to accept you will get lots of people who don't really want what you are offering, but amongst them all, you will find 'the one'. An absolute pain when you have to keep the house pristine and get out of the way, but the more you get through the door, the better your chance of selling, and selling for what you want for it.
Feedback though is incredibly useful. No good if it isn't honest though, and if people aren't prepared to say - as a pp noted - "i couldn't get past the smell of smoke" or damp or the rooms were a lot smaller than the pictures in the brochure suggested, or whatever. It is hard to hear about your home, but if you are wanting to sell, you need to know why it isn't selling so you can decide if there is something you can do about it.