Two separate issues.
First, we have added some anti-spam and anti-scam protections that keep new registrants from participating in the classifieds until their post count indicates that they are here for other reasons than those two activities. That low post count "switch" can be dealt with manually by request.
Second, posting your images in the galleries requires you to be a paid subscriber - it isn't very expensive, and it helps fund the site.
The other advantage of being a paid subscriber is that it allows you to start threads in the Classifieds, which means you can sell things here, or post want-to-buy threads.
In lolbertbread's case, with his/her/their low post count, it would make more sense to post a few more times in the threads (~15 or so) to get rid of the low post prohibitions, or to make a request that their prohibitions be removed.