In the part of Africa I am from, the challenge is cellular network providers sell data bundles specifically for WhatsApp. It is so much cheaper to buy a social media data bundle than generic data to use for browsing the web. As a result Telegram and Signal cannot compete. WhatsApp is literally the internet.
What incentive do network providers have to do that?
Sadly, when you're poor you couldn't care less about net neutrality if it means saving some money.