[MultipleParadox]

Exactly what Kaiu said, in my case
I wouldn't have a hard time believing a lot of them are also because people don't read though, because a lot don't, we have proof of this on a daily basis. I use to read everything twice or thrice, but heck, I recently posted a question myself without reading/searching first. It happens to all.

That being said, I think that it's also to make a first contact with seller as fast as possible, because some stuff tends to move so fast on the classifieds that by the time you read the ad carefully, another guy jumped on it and you lost the opportunity. Might be a factor there