Becuase 3/4 people are r-worded and so you need to make at least 7 friends to have a better chance of finding someone who also uses drugs.

In all seriousness though it's essentially laziness at its core. Switching to signal incurs a debt where you have to consider whether to continue using all of the other platforms where your privacy is not respected. This is an especially shit-uphill task today and as long as the majority that don't care about privacy can continue to live in relative safety, it's easier to dump on the guy that even hints at spending a metric shitton of effort on a task where your skill level is about on par with someone having just learned not to eat their boogers in public.