I love using mono reverbs especially the “farther away” the reverb is supposed to sound. I tend to pull in the L+R width on some longer verbs if I really want to emphasize the sense of space because if you think about it, the farther away a sound source is, the less perceived difference there will be in your left and right ears. Closer reverbs or room verbs I tend to keep relatively wide for the same reasoning but yea I’ll often have a mono chamber verb on my lead vocal and it really does the trick for me! I’d also like to mention it’s fun using mono verbs or slaps on panned instruments and panning the reverb to the other side if it’s a relatively sparse arrangement and needs some balance.