I don't really see the point. The largest image I have posted, is still under 2 MB. There's no point embedding larger images. If you really need a higher resolution, add a link.

I wonder what sort of image would need to be 5mb? I mean we dont need to be posting
large files like that, maybe on a photography website where people would be "pixel peeping".

And if accessing the forum through smartphone it enables us to zoom in if required for
more detail.

Essentially extra data means extra costs for storage.

There's always another side of the story.