But aren't reusable diapers better for the environment? 
Actually, that's debatable. Reusable diapers require a lot of water and, unless you're Alma, electricity and/or gas. However, I think I've read that they are slightly better for the environment, but not as much as you'd think. Most parents these days use disposable diapers (I did).
But beyond that, unfortunately people (including myself) do all kinds of things that aren't ideal for the environment for the sake of convenience. They drink bottled water, buy food in Styrofoam packages, drive cars when they could walk or bike or use public transportation, etc. So for many people, environmental friendliness is not the only, or even the top, priority.
I think it's admirable if parents decide to use reusable diapers to save space in landfills. But IMO the decision should be a joint one, at the very least reflecting the preference of the person(s) who do(es) the laundry.