I might be totally mistaken here, but I believe that the lack of clear economic incentives for Nostr relay operators can be a positive factor when it comes to deleting illegal content from their nodes.
As hobbyists primarily focused on supporting the Nostr network, they will take no risk by hosting illegal content.
To detect and remove illegal content (which can vary depending on local laws), they could employ AI tools. By fine-tuning these tools to be highly sensitive, they could ensure that all potentially illegal content is removed.
While this approach might lead to the removal of some legitimate content, the relay owners can find comfort in knowing that the decentralized nature of Nostr ensures that this content is likely still accessible on other relays. The network's redundancy helps to minimize the impact of individual relay errors, providing a safety net for content availability.
On the other hand, they will still gladly store controversial, offensive, outrageous, ... material. By doing so,
they can contribute to the diversity and openness of the Nostr network without damaging any revenue-generating business.