tv first had 2 screw terminals for 300 ohm antenna input on channels 2 to 13 (channel 1 was eliminated in '48).
then you needed a UHF converter box for those stations until UHF tuners were in the set (mandatory after '62).
then you might need a 75 ohm to 300 ohm transformer to take coaxial input from a CATV (early cable) system.
then you might need a converter box when cable came about for your tv to tune to it.
then you might have cable ready tv that could tune basic cable with no boxes.
early VCR were top loading and you might need a separate tuner box because it had none. if they had a tuner it often was worse than the one in the tv set and had VHF and UHF knobs just like the tv.
In addition to all the reasons stated above, a lot of people in the 90s era between the advent of universal VCR ownership and the coming of digital would definitely not want to connect everything through the VCR, because poorly-implemented Macrovision technology (designed to keep you from recording copyrighted material on the VCR) would destroy any signals routed through the VCR. Many early DVD player owners who didn’t upgrade their television to get more ports, on the theory that “we can just put it into the VCR,” found that the resulting image was totally unwatchable due to the brightness pulsing every few seconds.
Using the TV as the hub of the system and only outputting when you could record and wanted to do so made sense for many configurations. Now that a good HDMI-based receiver is $200 and no one bothers with copy-protecting anything, you should no longer do this unless you have to.
I have a Sony CRT HDTV from about 10 years ago that has such things. They call it “monitor out” and suggest it’s for use with two VCR’s and duplicating tapes, but that’s silly since you can connect two VCR’s directly together for such dubbing and not tie up the TV the whole time you’re copying the tape. I used to do that a lot in the 90’s.
It only works with analog signals, it’s noted. If you’re using the HDMI input or ATSC digital tuner, it won’t send those out the monitor out connection.
I’ve never actually used these outputs. I’ve only actually been using the TV at all for a week, even though I got it ~5 years ago off Craigslist.
I also have seen similar connections on a much older Sony, something from back when they still were making TV’s in big wooden cabinets that sit on the floor like furniture. I’m guessing that was was from the late (or maybe mid) 80’s, based on it having RCA jacks yet also being that cabinet style.
Sure, you wouldn’t really need to use it if you were duplicating entire tapes, but (as mentioned above), if you’re stitching together a little bit from this tape, a little bit from that tape, etc., it’s nice to have that monitor. Now, that’s probably a very niche usage, but it is something we used it for.