Imagine you signed up for a new cell phone plan, lets call the hypothetical provider 'superphone', and you put in your new sim card and tried to send an sms and it came back with a message saying "This user was not found on our network". You read the fine print and realise you can only call or send sms to people that also superphone sim cards. You immediately quit the plan and go with another provider, right?
Right?!
What about if your new email provider 'supermail' only allowed you to send emails to people with supermail accounts. Would you continue using the account?
So why are you still using Whatsapp, Instagram, Telegram etc.? The reason is these are products that were made after corporations realised that they could train people not to expect interoperability. Email and the telphone networks predate this development. Interoperability is the ability for different servers and platforms to communicate with each other over a shared protocol so that messages and information can be passed between them. For many people asking that Whatsapp be able to send messages to Telegram is a cool idea, but also a complex and difficult feature to implement. This is not the case. Implementing chat messages using a common protocol is asually easier and less complex than creating your own private protocol from scratch. Interoperability used to be the norm and the default across all platforms.
The reason companies stopped doing it is because they wanted to create monopolies. If you can send messages to all the same contacts regardless of whether you use the Whatsapp app or the Telegram app, and regardless of which company you register your account with, then you could quit their platform any time you want. You could switch to a competitor or an open source option. You could even create your own hand rolled chat application and use that. You would never lose the ability to communicate with your friends and you would never have to care what platform they are on. Social network corporations don't want that. Then they would have to compete with each other by offering you better software. They would have to have more and better features, better user experience, offer some kind of innovation that makes your life better. If they failed to really be better their competitors would overtake them and they would go out of business. With the non-interoperable model all they have to do is make sure all your friends are on their network, then none of you can leave without losing contact with everyone else.
When Facebook first added instant messaging, Facebook Messenger used the XMPP protocol, which was designed as an open chat protocol by Google (back when they still had "don't be evil" in their corporate code of conduct). This meant that you could send messages to people on facebook without actually having a facebook account. You could use a Google acount or even create a chat box on your own personal website that could chat with Facebook and Google accounts. This was because the engineers at Facebook were just nerds trying to create a chat program with the best possible functionality for the least possible work. At some point Facebook executives decided that they did not wan't their precious behaviour modification bubbles being interfered with by people they couldn't control and they put a stop to it. There was no outcry because Facebook users at the time mostly weren't even aware that their access to the rest of the chat world had just been cut off. Now we all just accept this as being the norm.
We need to stop accepting this. We need to abandon any platforms that don't offer interoperability. At least we need to harass them and ask them why it is not a feature. Otherwise we are just their domesticated herd animals. We will submit to being milked when they need our milk and if we moo too loudly we will be silenced.