I have Wireguard VPN configured on my Unifi Dream Router and have the client and cert installed on all my devices. Why would anyone need a travel router when they can just deploy the VPN app and cert on their device?

The only thing I can think of if you have a work laptop and you can't install the app but still want to connect to VPN for personal use but your work laptop should already have VPN client to connect to corp network for security.