Actually a lot of the audio gear of the 50's and 60's is built with similar build quality and parts as TV's of the period. Like audio, TV cant really be any better than the source, and NTSC is quite low resolution. Like it or not, most of us still rely on NTSC for most channels. You can blow it up to 40" if you want, but it looks terrible because of the lines. You have to add a line doubler (or represent the pixels digitally) to get a watchable picture at that size, and it still doesn't have any detail.
Worse, most NTSC sources are in some way flawed, they arent even as good as they can be. My 21" roundie is plenty good enough to show all the flaws in the local broadcasting here. Have you tried it? Tubes are tubes, and they are probably as well suited to other jobs as they are to audio, recognizing that they use more space, power, etc. There have been some real technological improvements made in TV in the last 40 years, but it is a surprisingly short list. When we all make the jump to HD that will change, but it's not even available where I live, let alone common.
One other thing you mentioned, build quality. I do like to have stuff that is built with at least above average, if not excellent build quality. Also, a lot of us work on this stuff ourselves. Most parts for a 60's TV set are still available. A modern set has IC's, and they don't make the same ones for very long. If a modern set fails at about two years, you will probably need a manual. If you buy it, and I should mention that it often costs more that the TV set did in the first place, you will probably find that you need an IC. That IC will no longer be available because it is 2 years old.
Hope this explains it
John