The "Add An Image" button in the below options would awesome if it actually let you add an Image!
Instead, when clicked, it brings up a script to lead to a website ![](https://) (Rather than let you upload an image)

You can just upload to https://imgbb.com/ and then copy-paste the code
I think I saw a post about switching forum software, if that happens you probably get native image upload.

By accepting user image upload and therefore image hosting responsibilities, SLR would be accepting a certain amount of risk and would have to implement controls to reduce that risk.
Only supporting URLs gives them some level of protection.

And, yes, they could implement robust forum upload monitoring, file scanning, and expand server space for image storage, but its SLR's business decision whether those costs are balanced by any true benefit.