That's...just not true, though.
You know what's still more valuable than our attention? Our money.
The only reason they want our attention is to get our money.
A big part of the problem is how many people simply don't have enough money, due to the stagnation of real wages and the increase in the cost of housing, health care, and higher education, among other things. If everyone had a reasonable amount of disposable income, as is true in a healthy society/economy, it would be much, much more viable for many websites and apps to charge for their usage, rather than being ad-supported.