This isn't the 60s. Superdelegates will never have the balls to overturn the will of the people, unless the primary is a virtual tie. So having them accomplishes nothing and simply breeds resentment about a "rigged process" every cycle. If PLEOs don't want to have to run for delegate slots, then just allocate them based off the popular vote. Easy.
Just look at the GOP. They could easily unbind their delegates if they wanted to and ditch Trump. But they won't, because they fear overturning the will of the voters would destroy their party. The same goes for the Democratic side, so superdelegates serve no purpose. Even in a scenario where superdelegates don't exist and Dems had the balls to do it, they could just unbind the delegates like some in the GOP are considering doing. There's no functional difference in having superdelegates and not having them, unless you enjoy the constant bitching about it every primary cycle. Do you really think 99.9% of people will care whether the will of the people was overturned by superdelegates or if the will of the people was overturned by the Rules Committee unbinding the delegates? The only part that will matter is "will of people overturned."
The clueless people (i.e some Bernie supporters, etc) would find something else to complain about, methinks. It's not worth it placating them in this instance.
It's not just a Bernie thing though. There was much gnashing of teeth on all sides about them in 2008 as well.