Say instead you play on the same table
Couldn't you lose 6 buy-ins one after the other?

If you were to say "But that would take a longer time" of course you'd be right. But playing multiple tables is a way of getting more hands in, whether you lose them or not.

The point is: your chance of losing 6 buy-ins is the same whether you play 1 table for 6 hours or 6 tables for 1 hour.