Why use TOR for a Bitcoin node?
For enhanced privacy, when you are connected to other nodes your IP will be exposed which can be a threat to your privacy.
But there are no direct advantages. No minor amount of Satoshis seem gained, meaning no financial gain. The disadvantage is the cost of the computer and storage space, and the cost of electricity and cost to cool my house.
There is no financial gain but you can't say there is no direct advantage while running your own node, cause you don't need to rely to 3rd party to validate your transaction. Also when you run your own node the privacy of the address and transaction history seems to be more valuable than few sats.