Carriers make a ' poo-ton ' of money from SMS. However, they get NOTHING when you sent a message to your friend using something like WhatsApp. You pay, in most cases anyway, a fixed amount of money for your data plan per month. So, basically..... you can send a million messages for the price of whatever you pay for your data plan.
I think you get the picture... carriers are Whatsapp online last seen tracker actually screwed out of some profit here. Should you care? Not really. It's there problem, right? It is.
Can carriers do anything? Yes, and in countries like the United States and others, they have. What they do is, they limit the amount of data you can use per month. So, instead of unlimited, you may now use 2 GB of data and not a byte ( or bit? ) more.
https://www.hacker9.com/free-whatsapp-last-seen-online-tracker.html