It's not like we can't do instant messaging without ads. I have used IRC every day for the past 15 years. Not every project needs a business model to work and not every approach is justified because the business needs it.
People watching the US Professional Football Championships primarily to see the ads and watching movie trailers voluntarily (which are ads) seem to disprove your suggestion.
Messaging has costs, especially if it includes proxying media, or verifying control of phone numbers. If the costs aren't too big, it's find not to have a business model, but if the costs are large, a business model enables longevity.
That's different to me than unsolicited advertising.
For instance, Instagram’s targeting has realized that I like outdoorsy products, and even though I don’t buy the products, sometimes they inspire me to find a way to recreate the item myself.
In my opinion your POV is very dismissive of all the good work product design foundries the world over have been doing.
The whole advertising industry is now predicated on gaming people's attention, wants, and financial vulnerabilities. I also don't see how not wanting to see ads is dismissive of product design foundries. Just because you've designed a good product does not mean you're entitled to my attention or my time.
And the whole point is they show me things I don’t know I wanted, so a search doesn’t solve the problem — I’d only search if I knew I wanted something.
Someone will always have to foot the bill, and telegram has been doing so for free for the last 8 years.