Why is Osclass missing X feature?
We want to make Osclass as flexible as possible, so when there are multiple solutions of vews about something, we prefer to left space for plugins.
Renewal: Renew a listing should have the same ID? a different ID? could an user renews unlimited times a listings? should we limit the renews per day/month/... ? Does renews cost money? how much? how does the user pay? ... There are multiple questions and configuration for this feature, including it in the core would make the admin more complex (lots of settings) and harder to maintain/develop.
Editor: There are multiple "editor" out there, from tinyMCE; CKEditor, aloha, webodf, mercury and those are the heavy weight, there are even more not so famous like froala wymeditor, jhtmlarea, squire,.... why limit to one? why not let you choose which one do you want/need?
Are "payments" important to a classifieds website? yes, but again, how we do implement it? there are many people asking for many different features and payment processors, including it in the core will not please everyone, make harder to maintain/develop/update, ... And this happens with a lot of features. Imagine there's some issue with some of this and you are required to update your whole website because it's a core feature.
I really would like to see more developers doing this kind of plugins