DW agrees w/Ardra (and I agree with her hubby) -- the washer and dryer are really great to have.
If Im at a rv park, I might just as well get my laundry done much quicker in the big machines.
DW starts a load, then goes and does something else (read, cook, watch TV, relax) until it needs attention again. Then places clothes in the dryer, starts it, then does something else again. I don't have to wait for her to get back or, on occasion, wait with her in the laundromat. There's no rush to get the clothes out of the dryer (or the washer, for that matter), as there would be in a laundromat.
And finally, DW can do one load, then another load another day OR, do more than one load in a row the same day -- it all depends on what we're up to that day and what she feels like doing.
Granted you can't wash clothes when boondocking, but you probably don't have a laundromat near then, either. And having a washer/dryer doesn't keep you from using a laundromat if you feel the need.
Still, some folks want the extra storage -- personal choice.