Ah. I interpreted you as saying "The ultra-rich have their money in 401(k) accounts", but it looks like you were saying the opposite -- that the ultra-wealthy are the ones *not* in 401(k)s.
I would think, though, that for 401(k)s to become a significant "piggy bank" to the rich, they'd have to represent more than the 1% your earlier "middle class holds 1-2% total" declaration suggests -- where it doesn't seem they could provide a boost to other accounts significant enough to even notice.
*sigh* 401(k)s... I'd like to like them, but...yeah, what could have been a decent idea was mutilated by restrictions in a way that nobody can like them. Give employees control of where they invest? Allow them to have almost anything they want inside of that instrument? Great idea, except:
1. The avg worker isn't exactly a financial genius, nor do they want to become one.
2. The choice is restricted to what the employer has to offer (unless you frequently change jobs, etc. to move funds out and into IRAs, but then those aren't 401(k); the 401(k) still stinks.)
3. Too many HR managers are stupid, lazy, or corrupt, and there are plenty of institutions and "consultants" ready to take full advantage of that, so your choices are often very poor.
4. At least in the old days, if a company's pension plan was bad they knew it reflected poorly on them. Now, they just point to the 401(k) and say it's someone else's fault it didn't work out so well.