We don't care how many one-on-one messages people send back and forth to each other if it's not unwanted.
The problem is there have been cases where spam bots (or even humans, actually) would sign up and send ads to all the forum members--even one at a time, despite a small limit on the number of people a single PM can be sent to--and in one case, a single spammer would repeatedly register and aggressively try to send up to the maximum of the lower limits we set. Recently I raised the limit since we hadn't, to my knowledge, had a problem with PM spam in quite awhile and I heard people were running into the limit. I'm not sure what the final limit will be--I didn't realize the limit of 6 was really an issue, but can keep it higher if people would like that.
