If they don't mine or produce blocks, why do some people run their own nodes?
First, the definition: a full node downloads the complete block data and independently verifies every block and transaction according to the consensus rules.
Here's why: client diversity is very important. If most nodes use the same client, a vulnerability in that client could affect the entire network.
On Ethereum, running a validator requires staking at least 32 $ETH . The current price is 2243.
Markets are always uncertain, so think ahead about what you'll do if your judgment turns out to be wrong.

#ETH

I'm just sharing my opinion; this isn't investment advice.