Exactly. These days, image files can be made pretty small thanks to compression, so even full HD images don't take up too much space - usually less than 2.5 megs and  that's plenty big enough for internet forums when most folks have 1080p screens or less anyway.  Bigger files would just eat up bandwidth and slow things down without adding anything useful.

After all, the whole point of this forum is not showing off hi-res photos that nobody can appreciate on their monitors.  I mean, unless you've got some specialty community for photographers or graphics work, do we really need massive images that take five minutes to load? Its better to keep file sizes reasonable so everything runs smooth and people can focus on the conversations.