> TV, newspapers and magazines supported themselves just fine using zero tracking on the advertising they ran.
False, false, demonstrably false.
Get familiar with concepts such as https://en.wikipedia.org/wiki/Call_to_action_(marketing)
Any business who places an ad may simply inquire of their customers "How'd you hear about us?" and they would be able to gauge the reach of a particular placement. Furthermore, anytime a coupon is published, clipped and used at that business, they are going to know where it came from, and so there's your tracking, on paper, no electronic voodoo necessary.
Now when we get to radio and TV, the calls to action were even more immediate and measurable. The stations themselves ran promotions where hundreds, thousands clamored to phone in and be the correct-numbered caller. The advertisements ran specials and promotions and "tell 'em Joe sent ya!" type stuff. They could give a special number or they could run at a special time. The business knew exactly what ad correlated to those callers.
Infomercials are classic calls to action. You purchase time, you run the ad, and you give an hour or so window for callers to get a great deal. The calls roll into your switchboard and you correlate them. Then you buy the next round of ads based on your successes.
I guarantee that there has never, ever been a time when advertisers were unable or unwilling to collect metrics on responses to ads. Especially when marketing costs money, that investment needs to be based on facts and statistics.