When I work on monitors, the last thing I do before firing it up to test it is to reattach the annode from the flyback to the tube. I often don’t get it right on the first try unless it’s one of the few tube+annode combos that gives any tactile feedback that it is in properly.
It doesn’t matter much now since CRTs aren’t being mass produced anymore, but I think if there was a “port” instead of the prongs that go in a vague hole, it would put less physical strain on the tube, make for better connections, and also be less dangerous to work around. Is the way the annode is connected to tubes in CRTs so inferior because of cost to construct an annode “port”, or because blowing the glass that way would make a better connection very difficult, or something else I am not thinking of?
I’d put this into the “It was good enough” category.
The only other option I could imagine would be a lug sticking out like the top end of a spark plug, but that would involve pressing on it hard enough to make the connection that cracking the “frit” seal where glass meets metal would be a very real possibility. (Not to mention being an easy target to get snagged when installing or removing the CRT.
Hooking a spring clip into that round ridge doesn’t put much stress on the glass, and for the five billion or so CRTs that have been made over the years, it worked pretty well.
A protrusion would also be an invitation to corona discharge.
passing metal through glass needs special methods and materials and is a failure point.
where the anode connection needs to be is hard to do. the tube needs to be annealed and have strength to hold a vacuum, having symmetry and gradual transitions aid that working well.