miners do include op_return txs for brc-20 because they pay competitive fees, making them economically valid from a profit perspective—not spam in that sense—but bitcoin's protocol validates only the data payload, not the "token transfer" logic, which remains off-chain and unenforceable by the chain itself.
it's financial activity in the sense of user intent and trading, but not native bitcoin settlement like utxo movements; the value comes from social consensus via indexers, not protocol enforcement, which is why it risks centralization.
bitcoin core docs