My use for it was to have a 5 way residential VPN across multiple Countries for obvious reasons. That wouldn't really suffice with just ssh. It also makes the shared infrastructure a lot easier to use for the rest of my family.
Also a globally accessible pihole connected to DoH which ensures somewhat global privacy.
They are basically my perfect use for my raspberry pis. Extremely low power, but perfectly capable for handling say 1080p video streams or to RDP into machines for access to cross-country resources.
The same thing that happens if the SSH daemon dies, I guess?
FWIW, I’ve been using Wireguard for a while (probably ~2 years?) as an always-on VPN for multiple mobile devices, and also as a reverse tunnel to pinhole service access inside a LAN. The Wireguard config and daemon has been rock solid. The only time it’s failed is when I messed up the AllowedIPs, but that failure occurs at configuration time. It has never crashed, or stopped routing traffic correctly, or otherwise failed in a way that interrupted traffic flows.
I have 5 locations running effectively independent VPNs, each hub connected to each other for redundancy if a VPN falls over.
i.e. Each hub has 1 VPN in, or is connecting 4 ways out.
If the port forwarding or something fails inbound, then I can connect via another VPN and try and debug/diagnose what is wrong.
If all VPNs are reporting down, then I know the pi/internet is completely down. It will either restart connectivity, but I have someone there who can plug/unplug/restore the system if necessary. The same kind of problem would occur if ssh falls over or wireguard.
ssh is typically the only thing i expose (publicly if needed) because in most environments were it is running it is used for troubleshooting issues. if your issue is that your wireguard peer cant connect you are lost with that suggestion.
But I find VPN a bit overkill on my personal machines.