Diversity has a value in stability of the ecosystem. Converge to a monoculture which brings highest short-term gains, and later it all can stagnate or even collapse for some single reason. See "banana monoculture".
For example, many distros only really differ from their parent in theming, replicated but differently named applications and so forth, which could all be offered in one distribution with less workload, but the same degree of genuine choice.
Same is true for DE's I think. Many of the things that differentiates DE's could probably be offered as configuration within one DE, with less workload but no or very little reduction in diversity.
If you want to get flamed to death, mention the word "configuration" on a Gnome mailing list.
There are people who think that things could just be configuration options, and then there are people who insist that the default configuration should be right, and that too much configuration is detrimental to the user experience (because it's hard/complex/time-consuming) and to development time (if you have two sets of two configuration options, that means you have four configuration to tests, and so on). It's not like these folks don't have a point, either.
Perhaps if this DE is KDE. Gnome devs aren't interested in a configurable DE.