Adding images to DMs isn’t as easy as it sounds.
They need to build the UI, add the upload logic, a place to store them, and add correct access controls so people can’t see other peoples images.
This site's been around for three and a half years. Speaking as a web developer myself, that shouldn't even take a competent team three and a half months.
I am aware. It's been two years since DMs were first introduced, how long exactly are we assuming it should take for them to figure this very common social media attribute out?