I think it just depends on the person. I have mine for meat and eggs. While I am not going to cull after their biggest production period is over (about 1 yr) I don't see keeping them forever. I already process extras. I do have 2 two year old white leghorns that were my first aqcuisition after we moved her last June so I could get some quick eggs. They still lay just about every day but there is a big difference in their eggs compared to my younger birds. The whites are runnier and the yolks are paler. They will be the first to go when I'm processing to reduce numbers. Currently they are just providing breakfast eggs as they are too quick for the roos to catch (haven't seen a fertile WLH egg yet) and they lay the largest egg.
Personally, I think that many people want to keep their chickens forever but the chickens will really change in their egg laying ability and if someone can only have 4 or 5 chickens due to laws, keeping them, without eggs, for 6-7 years is unrealistic.