Totally agree. WhatsApp was the last one I deleted, too. Not long ago actually. Luckily my family gave in and co-installed Signal, which was my main reason to stay at WhatsApp.
The function of Signal that scans your address book and shows everyone already using it when you first run it can be a good hook, if it shows results 😆
So secretly getting 2-3 people in your bubble to use it first and then let others discover that they are using it can be a tactic I guess 😅