Myself and my friend made new accounts yesterday even though my friend is already 50 in all ranked lists as well as being a 5 Star General and i have 50s in TS, TD, Snipers and MLG it does get a little boring after a while, our 50s are essentially 'rank-locked' since we have played on them quite a lot, too much in fact! (i <3 Halo 3) and so getting exp alone is getting boring, the games are competitive but since most of the people we play are more or less 'rank-locked' themselves, winning/ losing doesn't give me the same high as it used to.
While last night and earlier this evening we have mostly been in Team slayer and have not lost a legit game yet (2 losses due to derankers, surprised they still exist with Halo 4 on the horizon...) and between us we have averaged nearly 20 kills each with some stupidly unfair end results (50-8 and that was a 4v4) we both admit that while we are crushing lower ranks with hardly any effort it really isnt fun until we get to the 40+ range.
Personally i'd love to avoid playing against the lower ranks as for me if it isnt a fair challenge then it is boring and on top of that im essentially reducing the persons i match up against's enjoyment of the game.
But really doing 1-50 over and over again is really fun for some people, i personally love it, it's too addictive (i have 24 accounts for Halo 3 now >.> )i would not say all 50s make new accounts solely to destroy lower ranks, some may but personally i think, like myself, they too enjoy doing 1-50 all over again, well except for the ones getting boosted of course :p
I suggest you avoid any players you believe to be too good for the current skill bracket you are in and hope for fair sided matches more often.
Finally if you have run into NolansRoadToH4 / RaritysRoadToH4 tonight in Team Slayer and were on the opposite team then i apologise! :) but on a serious note i would like to say that anyone has the potential to be good at Halo if you put the effort in and allow yourself to learn some new things then soon yourself will be destroying these new account 50s :D