Smashwords is the evolutionary equivalent of a housefly. Very early on, it carved out a comfortable little niche for itself and has continued unchanged ever since. It has survived multiple extinction-level events and will continue to survive such calamities in the future, but will never be anything bigger or more complex.
I'm still on Smashwords, but I don't distribute anywhere through them except their libray direct program. Too many problems. For years, I used them to distribut to the places that Draft2Digital didn't go yet, but I never saw a single sale from it, so I figured it isn't worth the trouble. With that said, I do see a trickle of sales from the Smashwords site itself, and if I don't publish a book on Smashwords I will get emails from readers asking why it isn't there.