Yeah, I hear what you're saying, I typically work with at least 4x mon mix rigs as well, but I don't sing any lead, so I tend to move around a lot, so that doesn't really work for me 'cause it's way too directional/local to one spot for my "focal mix".
Now, if all I ever wanted to hear was a "general" mix, that'd probably still be ok, 'cause you're always close to someone's monitor. However, I find when folks have their own mixes, their part and/or instrument is REALLY prominient and the rest is mixed back quite a bit. That doesn't really help me monitor me much at all. While that's not a necessity, it's definitely my preference, as I like to be able to focus more specifically on my contribution sometimes as well. I find firing my bass cross stage works best. I don't bother the singers much, and the guitar(s) and drummer seem to be able to lock in with me a bit better for having more of a stage "presence" vs what's mixed in with their monitor.
Plus, I like the ability to adjust my tone on stage... understood, it has no bearing on what the audience hears, but if I'm happier with what I hear, I play better. Maybe that's just me, tho.
I find it works best for m
You're right tho, it can work, it's just not the way I like it.