I was early 80s, and watched landline and mobile costs fall to negligible levels.
My current girlfriend was born in the late 80s (USA, but world traveler with family work), and I think from the start of highschool onward pretty much always assumed there was an internet connection and too-cheap-to-care calls even before everyone made their own VOIP/video chat messengers.
Something that came with the Internet, and didn't exist for me prior to its existence, was a large body of friends who were not local to me. Today, if I had to go back to metered long distance rather than what we have today it would absolutely be cost prohibitive! And clearly some people move around more than others and for them they might have a lot of friends and family outside of their local calling region back then as well.
The bottom line is that I can see the point you were making but I think we disagree on the magnitude of its impact on the general population that was living with phones at that time.
In much of the US, in the 70's, 80's, and 90's a telephone had a fixed monthly fee and 'free' calling to any other phone in the local area. Phone penetration was over 90%[1] in 1970 and rose to over 95% by 1980 suggesting that even those at 50% below the poverty line in 1980 (roughly 6% of the US population) had access to a telephone.
So for many living in the US they have probably experienced being able to talk with all of their friends for "free" as long as they want, and if they were old enough arguing with siblings about who got to use the phone longest.
Further, in the "current" epoch, the article suggested that WhatsApp was profitable at 99 cents per year when it was acquired. I would not be surprised if that it is still the case that such a messaging service does not require advertising revenue to be cash flow positive. It just needs enough subscribers.
[1] https://www.statista.com/statistics/189959/housing-units-wit...