"Why bother recording over the air?"
1) Something with the line-out connectors
2) The needed cable(s)
3) Something with the line-in connectors
4) The knowledge about how to do it - which is very simple, once you know it.
1) and 2) may not have been both available in the devices you owned. 3) could have been also an issue when there were far less electronics stores - no onlinge catlog - and hi-fi were sold in specialized ones. 4) was also an issue when you were a young teenager and there was no Internet and Google to answer to all your questions.
My first non-fully-toy deck came with a complex DIN plug - the manual had a full wiring diagram and explanation of what every pin did, but I wasn't able to understand it... nor I knew where to get one of those plugs - I was eleven, living in a small town.
But it was funny when some years later I gave a schoolmate a tape recorded directly from a turntable to cassette on an hi-fi system - he said the recording was not good as his ones - I made a big laugh when I saw later he recorded putting a single, mono mic in front of a single speaker.... exactly because he didn't know how to connect the devices in any other way.