Many companies face that choice. What I will never understand is why anyone would use a service like that to organise protests against a government that can enforce its censorship rules.
Scale effects. Everyone I know has Whatsapp, some have Telegram and I can count the number of Signal users I know on one hand. It's easier to get a mass protest done via chainmal in WA/Telegram than via Signal.
Also, organising a protest isn't about keeping individual messages secret. You can never keep something secret that you want thousands or hundereds of thousands of people to know about. It's all about getting the message across fast without the government blocking it.
Email is the only reasonably decentralised and diverse messaging infrastructure we have. It's impossible to block without shutting down the entire Internet in a country.