Interesting article. What the companies bringing out Micro-Cassettes failed to grasp was that it was all about the media. I know 8 track was more popular in the USA, but by the 1970s Cassettes were a very popular medium, especially in cars with pre-recorded ones being readily available and many music centre type stereos incorporating tape decks. To prove the point here is a UK catalogue listing from 1974. Interesting that some top artists like Donny Osmond aren't even available from them on 8 track while the price is higher for cassettes and even higher for 8 track cartridges compared to LPs. With something like item F on the second page you would be all ready to start making cassettes for your car five years before the Walkman was launched. I would guess that most people who bought the first Personal Stereos already had a stash of tapes and suddenly saw an opportunity to use them outside of the home or car. I didn't get one in 1981 as I was spending my money on my first car and a Motorola tape player (which cost much less than a Walkman) to go in it.
If you were lucky enough to own a music centre you could buy three C60s for £1.30 in the same catalogue to tape your LPs. I wonder why they later thought "Home taping is killing music" ? Interestingly there is also a blank 8 track cartridge in the catalogue. £1.99 for a single cartridge. No wonder 8 track was dying.
