It isn’t. I’ve personally had it happen where a relative who went to some country that bans video calling and VoIP (except for the unencrypted/honey pots of course) and used Signal to call people back home (only because I told them it would be unblocked due to censorship circumvention). Despite everyone in my household being familiar with WhatsApp, I was the only who did video calls with them and had to share my device so others could also call them. Even when I’d set up Signal on one of their devices, they still complained it was to difficult to use, insisted I’d uninstall it when the trip was over and used it a grand total of once.
I honestly think it’s partly to do with the nerd factor. This same relative turned out to also have installed the backdoored unencrypted app to chat with others, but hid it from us due to me being vocal about not using that. These other households, also WhatsApp based, managed to install, sign up and use that just fine. They also couldn’t be bothered to set up Signal for some reason, yet gladly accepted the suggestion to use the honey pot.
I think that these people in my circle don’t care about security at all and only care about the platform. If it’s “secure”, “private” and “censorship resistant” and they haven’t heard of it until I, the “techie”, explain the technological benefits of it, they’ll think it’s a niche “techie” thing they’re not nerdy enough to understand. If I get them to use it, they’ll keep thinking this whenever something is slightly different than WhatsApp and be frustrated. Meanwhile they can get behind the honey pot because “WhatsApp doesn’t work there, this is just what people in that country use”. It appears normal because “normal people” use it all the time, and they’ll solve any inconvenience themselves because “normal people (can) use this, and I’m normal too”.
There already exists a “Google Play licence check” permission apps can use to verify whether or not the app has been bought on a Google account that’s present on the device.
If people can crack the app to remove this (which is a thing for some of the popular apps), they’ll also figure out how to patch this out. This is strictly useful for free apps, and only serves to make it unviable to distribute verifiably clean apk’s outside of Google Play (so rip APKMirror)