You have all valid points, but I just want to mention a lot of the time growing up, we had many family functions, and went to many events, a lot of these were filmed on VHS Cassette tape. You can not find this content online or on steaming sites or on dvd or elsewhere. Some people just want to watch it a few times, maybe they are not interested in converting it or archiving it for long term arhcival. its entirely possible for someone to want to watch an old vhs tape of a hockey game and not want to convert it even if the tape is near end of life.
Converters are available yes we know, but they also reduce the simplicity and add a complex layer of installation to the tv. some people just want a tv to plug something in and go. yes tvs can be found with composite inputs, but if you go to the big box stores, or electronic stores, you wont find those TVs, everyone wants to sell you the TVs that only have hdmi inputs, and besides, if someone does have it, good luck trying to see it in person, it will most likely be a special order or internet order and you wont be able to see the device in person.
Not everyone wants ot play emulators, We found a classic video game console at my parents house and it works, we also are happy our tv set has composite inputs.
yes we also know blue ray players play dvds, but if you have a dvd player are you really going to go out and buy a blue ray player? sometimes people only think of logical answers and does not think about the financial aspect too. lets face it, if u want to use older devices with newer tvs be prepared to spend $$$ on converters and adaptors and new blue ray players, because a lot of people will just say "buy this or that" to solve the problem, maybe because they do not know what it is like to be in someone elses shoes