I am typically one of those on almost any server who still level in Bichon or BC while some are in 30ties or even hitting lev40 and I wouldn't like the idea of being jacked up level and item wise to close the gap with the server sharks.
I would feel it cheapens, devalues even that lesser effort I put in if that was done on some continuing basis. I believe it was on 5Heroes high rate server when on two or three occasions, I stopped playing for several months, then I logged in and found starting level was higher than I was at when I left, so I was boosted to it. It was accompanied by a gift of some crap items, my old ones were always better. I could live with it because that happened only once in a long while, at major points of server life you might say. But to be getting handout levels/items on some more continuing basis, it might make me feel like there is no point in grinding it and I would feel there is no point in playing.
The lower the rate, the more complete should lower level areas be, have variety. Maybe closest came Primordial server I am on just now but even that skips some features that euro had towards its end of life, like it has connection paths but they are limited in extent, there is no magic cave I think, no casino, on the other hand it seems to have way too much variety of ores, just reading the list on patch notes makes ones brain boil. It is fairly low rate but palatable because you get skills at lower levels than is standard, which is very much welcome.
You want pple to socialize, but social groups mean pple don't play solo and so gain huge advantage of those who play solo. This is where I see big incompatibility, solo vs group play style.
Also, majority of those who put up servers tend to focus on their favorite class they played in past on servers and it shows. Bulk of servers are put up by veteran wiz players, maybe also tao, war is rarest I think. You see it right away on videos or screens when they develop, advertise their server. And that is hard to get away from your fav class view when making a server. That said, maybe some who put up server are universals, not favoring one class over another.
Also, everybody always has full mouth of concerns about the tail levels on their server but ranking is almost always sole affair of top 20, maybe you get what I am trying to say by that.