Why is most of the stuff in the marketplace not compatible with unreal engine 4.9?

I’ve actually been very curious about this since my first pack. I have never submitted a new version, but the marketplace eventually gets updated to say they are compatible with the latest version.

I check my packs to make sure there arent any problems, of course, but do i need to start submitting updates now or will you continue to just update the compatible version numbers if there arent problems?