Money/profitability.
As an example, I’ve got a quadraphonic 8track player. It uses 4 pickups in the head instead of the standard 2:
As opposed to the “standard” 8 track head:
Which means the quad head moves 1/2 as much as a two pickup head and uses a relay system to get all 4 programs (8 tracks). It physically moves between programs 1 and three and then uses a relay system (to switch over which pickups its using) to get programs 2 and 4. Each program uses two tracks to get stereo, which gets you to your “8 track”. Quad cassettes only have two programs (4 tracks each).
That quad head is pretty packed with pickups, you can see they are much smaller and I can’t imagine 1960’s/70’s manufacturing processes getting 4 more in there without other problems. Its a size thing. They probably could get eight pickups in there in the 70’s, but it would probably be (had been) prohibitively expensive and 8 track was really meant for cheap, mobile applications.
Logically, you would think just make the tape wider, but then everything gets bigger/more expensive and 8 track was meant to be a “mobile“ format. Size begins to work against you at some point and 8 track players were already pretty big chunks hanging under a car’s dash.
I’d guess by the time they had gotten something like an 8 pickup head rolling (manufacturing wise), compact cassettes would have been coming on strong and that killed off 8 track anyways. Making an 8 track player more expensive would have just killed it off faster. There are other reasons why CC killed off 8track (and good reasons) but thats a topic for another discussion.
You also have to remember 8 track was originally designed by Lear for use in Lear jets so their (fairly exclusive) passengers could listen to something besides the sound of air screaming past the fuselage. “Quality” sound was neither intended (nor would it have been applicable) in such a noise filled environment. Tape wind up and deteriorating highs would just mean tossing the tape and getting a new one as a business expense so they didn’t care about those issues. A private car owner would a different story though.…wallets are not bottomless like a luxury/business venture like private jets were/are.
Industry seldom reinvents something if it already works, so 8 track simply transferred over “as is” from aircraft to road cars….along with its limitations.
The other thing is that manufacturing was still more comfortable with making “mechanical” movements back then: wind up wrist watches, desk and wall clocks, kitchen/home appliances, carburetors and mechanical spark advance, etc.
Digital “trickery” was still relatively new and comparatively expensive. It was also still relatively primitive compared to today, mostly using discrete components rather than todays powerful “chips”. I still remember the first TI red segmented display calculators being a “wow” thing and expensive for that time (anyone remember spelling “boobies” and giggling?). It also wasn’t too long before that time that a computer would take up an entire room, or even a building. Mechanical movement's were just easier (Ie:cheaper) to build and control.
Even my quad 8 track player uses relays to change two of the programs and relays are electro-mechanical devices, subject to the possibility or both electrical and mechanical failures. I’ve had to pull the orginal relays and replace them with modern ones in an external network because the originals had failed. Yet anther reflection of the tech of the time being more comfortable with mechanical movements, meaning it was more affordable to build. An 8 pickup head would at least double the twin relays and associated circuit components. Which would mean more design, more components and circuits, more points for failure.
And with that we’re back to the “money/profitability” reasons.
8 track just carried within its very design the seeds of its own failure. 8 pickup heads would have just sped that demise up.
To say nothing of all the 8 track tape you’d find tossed by the roadside in the 70’s because it had balled itself up in the player and had to be literally “ripped” to get the cart back out….
