"Uncooperative" sellers have a number of reasons....
Out of touch with the market
Don't really want to sell
Tight "sellers" market
Frustrated with the process
The last "sellers" market I saw was in 2006. Coincidently, I also saw the most sellers frustrated with the process at the same time.
Something would get posted and they'd get swamped by brokers trying to be "first". I saw one 177 posted at 8am. I don't like calling people early in the morning so I waited until 11am. The seller, an older gent, had already pulled the airplane off the market because by 9am, three brokers had already gotten into a fight with him over who was "first".
By the time the market had chilled in 2010, I found the most sellers disconnected with reality. I offered one guy what was really an above market price for his Dakota (it needed a few items which I was willing to eat because it had a specific avionics configuration that was not mainstream), and he told me he'd cut it up for scrap before he sold it for that. The price he quoted me was about %10 above the 2005 value.
Brokers of all types can be hysterical. I checked out another Dakota that needed some TLC...nothing serious but would have taken 20-25 hours of A&P time to clean up various items plus some parts (mostly some inop items). I was a cash customer and wanted to work with them, but they tried every newbie trick in the book including "we'll have our MX to do the pre-buy". I finally got tired of their shenanigans and walked away.