Backwards compatibility is seriously under appreciated. When I tell developers to ensure that their changes are backwards compatible, they tend to look at me like I'm green.

I do not understand the disconnect that developers have with understanding all of the benefits that it brings. Yes, you have some extra code in your code base so it's less clean. You also have a stable environment as a result. The first affects only your personal preference. The latter affects all of your developers and users.

Unless you have a situation where it's impossible to maintain, not insisting on it is pure self interest.