Let's see, Signal is based in the US. Wechat is a Chinese system with a great UX that is based in China. Telegram used to be based in Russia. Whatsapp is owned by Facebook.

I think it is pretty self-explanatory that in all these countries, governments haven't been exactly subtle when it comes to their efforts to intercept communications. In my mind, Telegram is the only software that resisted such interference in an almost heroic way and ended up having to move out of the country.