It is probably largely just the ones that one can get here, rather then the breed in general; and my set up.
The first two I got were Cuckoos, and looked very well bred and everything. One hardly ever laid eggs, and they were always wonky and thin shelled. I had to put her down at 8 months old...
I have;
Light, Coronation, and Speckled Sussex
Cuckoo and Buff Orpington
RIR
Golden and Black Copper Marans
And lots of home bred mixes of those breeds.
The coronation Susses are my all time favorites, due to our healthy they are, their temperaments, and looks. Also a very good duel-purpose...