Deciding on a product design that's easily marketable is also a marketing problem.
You suggest adding it as a "bonus", but for whom? Recording what on the walk? How would you advertise that along the main feature people actually buy the thing for? If not, what purpose does it serve? It's a few cents, but that's still a few cents too much if that's not what you're convincing people to buy.
Try to think of someone who didn't buy a walkman because it lacked a recording feature. What's their story? Can that easily be represented in the marketing material?
This thread reminded me of Blaise Pascal's quip "I would have written a shorter letter, but did not have the time."
It's often easier to just throw in everything that's easy to do with little thought about cohesiveness or user experience. Leaving the record feature out of the walkman was likely a more difficult idea to push than including it and I think they were right.
Exactly this. You wouldn’t make a dictaphone and then be like, shall we just tout good speakers in it just in case someone wants to also listen to their music on it. So why the other way around.