Network effect. The key though is that Telegram actually isn't free to consumers when compared to Whatsapp. At $1/year + access to everyone who is already on

Network effect. The key though is that Telegram actually isn't free to consumers when compared to Whatsapp. At $1/year + access to everyone who is already on network vs. $0/year + access to smaller network+need to invite your friends to build that network Whatsapp is actually (significantly) cheaper. If it was more expensive per year I think they'd be giving some room, but no one is even going to notice getting billed.