It to me just seems easier and safer to have the rules in place as asked for.
On the Skyline forum you can stuck stuff up for sale without photos and all you end up with are members posting numerous posts asking to see pictures, which the seller then responds to via a PM, probably dozens of times, surely for the sellers sake it easier to just post it up once on the thread? I don't understand the logic not to do this it just wastes everyones time, no one is going to buy stuff blind, there might be the odd occasion but generally people like to see what they are buying.
As said previously, you are getting a free space to advertise stuff for sale to targeted customers - not many places you can do that so effectively. The rules are not difficult, taking photos and posting them on hosting sites is as easy as signing up and posting on a forum - can't see how that is a problem.