> we lose any ability to know who the “real” person-user is on top
It's a complex topic probably best suited for discussion elsewhere, but do we even need to discern that anymore? Statistically most Linux systems running now are single-seat (as in, one real user).
A big corp with thousands of servers and employees might want to know this stuff for audit logging, but if employees have root access, they can already fake everything at ring 3. Big corps use security software that do that stuff in ring 0.