The old devices are not deliberately restricted. I usually buy an older device that suits my needs instead of a new one for this reason and because if is easier to repair when it does fail.
Let's say I have an old tape deck. It is what it is, the sound quality or functions are not artificially restricted. If I want to I can improve it beyond the original specifications, but that requires modifying it. Same with my car - if it does not have some part then it doesn't, if I want to I can install it and use the new function.
Compare that to, say, modern phones. Android is very similar to Linux, but I cannot get a root shell on my own phone (without modifying it) even though it is physically capable of this, but that feature is restricted by the manufacturer. For example, I have a video file that plays without sound on an Android tablet because the sound codec is not supported. Decoding sound does not take a lot of CPU power, so I should be able to just install the codec as I can do on a PC, but it is restricted.