I see where you are coming from Dave. To your point, yes I think the vast majority of ESOP companies either have a separate 401k, or they manage a combined retirement plan where a 401k is bundled with the ESOP. So in that sense, the ESOP really is additional on top of a 401k.
I agree that a firm that offers an ESOP as a supplement could have a very powerful retention tool on their hands, and probably avoid a lot of conflicts with their workers. Hopefully, the more engaging work environment created by, or supported by an ESOP, would create other synergies with real, positive, financial impacts.
I have probably seen too many tech firms with brutal quota systems, and a policy of letting go double-digit levels of "underperforming" employees every quarter. At those firms survivors receive higher quotas, single-digit salary increases, and an impressive sounding title bumps every year.
For firms like that, retention is the last thing on management's mind, because cycling through new workers is so damned profitable.
The attrition isn't a bug. It's a feature.