it is true that's all nostr is (well, mostly...it also does some data caching), but there is a saying I try to keep to heart:

if you offer something free, people will take it

nostr relays cannot offer free bandwidth and storage forever because (1) those things cost money, which is a scarce resource (2) bots will consume all of the free bandwidth and storage you offer, and by extension they will consume all of the money it costs you to provide those things for free, until you run out of money, at which point you must cease operations

in order to survive and escape/avoid that doom loop, relay operators must ensure that their income exceeds the aggregate costs of bot activity on their relays

rate limits are one way to help with that. They help keep aggregate costs low and predictable

so by having them, "free relays" aren't "using it wrong," they are managing their costs, which is a precondition for sustainably offering a service for free. No service with unbounded costs and unreliable income can survive long, therefore rate limits are a survival mechanism

but it has consequences: stuff that needs to go beyond the standard rate limits (like the frightening network) cannot rely on free relays

users would need to register with a paid relay, and that sucks...or at least it feels like it right now. I have a feeling though that paid relays are actually a good thing, and are the very thing that will ensure nostr's success in the long term