You can do some cool stuff with stereo, it's just not required to get good sound, imo.
Lot of cool keyboard effects to swirl around or ping pong back and forth. Anything else with a chorus or a flanger on it too.
Some types of vocal reverbs or snapback delays, echoes, etc.
A small amount of panning can also help get separation between similar/same instruments, like 2 guitars, but I've heard way too many people go overboard with it. End up with just the slice up the middle of the closer audience getting the full sound while the folks on both sides hear it too far out of balance. One guitar overbearing while the other way in the background, etc.
A lead should usually be panned back to the middle which pretty much requires a dedicated mix guy to do.
None of that really necessary imo if their tones are more complimentary instead of competing.
Of course the drum fills that pan right to left as he goes around the kit. Need a knob guy for that one too else you get the same too far split problem during the rest of the song.
For a DIY band, and especially mixing from stage, mono and complimentary tones / self mix slotting is the way to go.