It’s my understanding that one can arrange for oneself (and family members) to be employed by one’s businesses such that 401ks are maxed out. This can amount to a huge de jure employment benefit but a de facto slow-motion tax-advantaged inheritance over, say, 20 or 30 years. Just live off trust assets and the rest of your wages (or whatever) until you can draw on retirement.

Though yes it’s probably too small-potatoes for the rich rich to bother with. Mere tens-of-millions business owners are more the audience for that maneuver. Like everything else it seems one is likely to be smacked down for attempting to use it while not-rich (need enough legitimate business activity to make the wages to relatives plausible)