The way I look at it: a Nuc is a temporary arrangement. If you just leave them alone, they will fill up the box and promptly swarm. So you have to be removing frames on a regular basis to make it work. Nucs are nice for building comb, banking queens, bolstering weak hives, extra income. They are in no way a replacement for a full hive though. A full colony (two deep boxes full of bees) will produce a full frame of capped brood about every other day. A Nuc takes about 10 days to do the same. A full colony can draw out a frame of foundation in about two days, a Nuc takes about a week to do the same. Nucs are more likely to: get robbed, overheat, get chilled, starve, and swarm.
I know lots of people manage Nucs just fine, but for me I'd rather have 3 weak hives building up to becoming full hives than 3 Nucs constantly in need of attention.