Having a vote means that you, as a node runner, can choose to follow a specific protocol. If someone tries to send you bitcoin from a protocol that has a different supply, you can reject it. If people try to change the code, you can object to that and run the code you agree to on your node.
If you don’t have a node, you’re not a peer. If you’re not a peer, you rely on a peer to relay your transactions and tell you the state of the network. If you, without a node, don’t like a change, you can’t really express your disagreement because you’re not a peer and you’re not in charge of what code is being run by the peer that’s relaying your transactions.
Hope this helps, but do ask AI