Blockchains are public ledgers and exist to achieve global consensus on transaction ordering, and that matters when it comes to money but not when it comes to social network posts. Blockchains are also inefficient as databases, and would require relays to maintain a copy of all the events on the network in order to remain in global consensus, whereas with Nostr they only need to store the events associated with the users connected to them. The need for money ona social network, is a different question, and in that case Nostr uses the best money for the job, and also allows anyone to build/integrate support for other monies if they need to because the underlying communication protocol is not tied to any particular token/money. It’s a better way to do social networking.

It would be a little bit like asking why eBay or a local farmers market doesn’t have its own internal token. Simple, it’s not needed. Money already exists in many forms, and we’re not trying to recreate money here. We just plug money into these things where it makes sense to have money part of the experience. Non-money activities don’t need a ledger or token in order to occur.

The toxic answer is that their token would be a centralized shitcoin scam meant only to enrich its founders. 😁