There are many occasions where you need to create connections to machines and services that are protected by firewalls because it is appropriate to adequately protect them, but for which the creation of a VPN becomes an excessive burden. For this reason, the ability to port forwarding via SSH is very useful for creating an encrypted tunnel from one machine to another, allowing you to enable only local access (such as a MySQL only listens locally) safely, with the only the problem that in case of problems, the SSH connection (and its tunnels) could fall.