To me, Nostr is a signed messaging system, not an event logging system. The relays are just databases (quite literally). Just as with other databases, sometimes you log stuff other times you overwrite things. Depends on the situation. That’s been Nostr’s approach since the beginning. Kind 0 & 3 are replaceable. Kind 1 isn’t.
Discussion
The more decentralized a system is, the worse it gets for state storage because clients must achieve consensus on the state at every point in time.
Even though you could choose to have state, the bigger your "micro service" structure is, the bigger the need to save events individually and sync the later. That's what a relay does.