What is funny is that my younger brother is a "metric" guy.... crazy smart (was an engineer at Ford, Rover and SAAB) and has built some ridiculous cars (big time Mini and Audi guy) but when I bring up welding he brings up adhesives.
I'm sure it has its place and can be very effective. Would be most curious about situations where the surfaces arent in perfect contact.
A beauty of welds is they can be as strong with just a line of contact - like that washer welded into frame's body mount bracket.