You might be genuine yourself without a nefarious agenda, but there are hundreds maybe thousands of pimps, prossies, "boyfriends" and failed forum owners who create accounts to pose as punters so they can PM other members, gain their confidence, find out who they are and then out them / threaten them / etc. As well as stalker fluffies PM'ing punters who've posted about a prossie they've become obsessed with. These things have happened so many times. For that reason the minimum criteria to gain PM access is quite high, new members don't automatically get it with zero posts like they've done so for 7+ years. And it is set to get extremely high later this year. A drop from current 3% to just 1% of accounts having PM access.
It's a shame to put these restrictions that affect genuine punters, but I feel necessary. I have come to regard PM facility and access to Off-Topic as extra luxury. The most important part of the site - posting and sharing info publicly - is still open without much restriction.