I don't think I'll be dumping any matches on purpose as I'd like to play 4.5 though I can see the allure of staying at 4.0. At my club, there are ~350 tennis players and only ~9 4.5's (10 next year as I think my 11-1 (got cheated in a third set TB to break my unbeaten streak - oh well) record will put me over the edge).
At 4.0 you can easily play:
USTA 4.0 on 2 teams at the same club
7.0 mixed (I pair with my 3.0 wife)
7.5 mixed
7.5 combo
8.0
8.5 combo
8.5 mixed
--------
8 teams
At 4.5 given the # of players at that level, you're more or less stuck at:
USTA 4.5
8.5 combo
------------
2 teams
We have no 8.5 mixed team
All the 7.5 teams become a bit of a challenge in pairing with a 3.0
We don't have enough for 9.0
So I see the allure, but prefer the better competition at the 4.5 level.