In some cases, it is...
But I think, most times, it's the equivalent of getting something you ordered online, encased in a large blob of jello.
You can look at it, but everyone is going to have a hard time interacting with it.
Is there any guarantee that even reddit will keep around image posts uploaded to its own servers, forever?
Personally, I still prefer links as I find them easier to sort and categorize in my bookmark library, or indeed take screenshots of the linked content if I deem it worth of it.
As it is with images, I don't really bother to sort them so I have them scattered all over. In the folder where my SMS app saves images, in the folder where whatsapp saves images, in the case of discord I rarely explicitly download and save the images outside the app, etc. Opening a link I receive opens the link in one program, my default browser, from where I can manage the link as I see fit. All these different apps have their own built in image viewers, save locations, or layers between the message and the content/image, making it much more of a hassle to manage that image as compared to a plain link.