- Privacy. You don't need intermediaries to load up your wallet.
- Security. You don't rely on third parties which might serve you incorrect data (with inability for verification). Also, privacy equates to more security, because there is risk that is mitigated.
- Minimum bandwidth benefit for the network.
- It allows you to run a lightning node, which you couldn't do safely otherwise.
What a full node does NOT provide:
- Vote. You don't vote for the network. Running a full node is procedure that concerns the one who does it. Voting for the order of transactions is done with Proof-of-Work, and you only get to enforce that rule. You can neither vote for the denial of a transaction, nor can you vote for any other consensus rule change. If you want to change consensus, you're free to do it regardless the people who will agree (as in Bitcoin Cash, Bitcoin SV etc).
- Impressive bandwidth benefit. That would be the case if there were very few nodes; there are currently about 13,000, far more than needed for a network to operate.