Comic Sans’ message is obvious, it’s easy to pick out in the long list of fonts in Word and has a memorable name. It’s obviously and painfully friendly and playful.
How are normal people supposed to be able to tell that a font like Georgia is also much friendlier than the angular and rickety Times New Roman while at the same time being entirely appropriate for nearly every imaginable formal setting (unlike Comic Sans)?
Friendly fonts exists on everyones’ PC, it’s just that Word’s font picker doesn’t allow you to tell the difference at a glance unless it’s really obvious like in the case of Comic Sans.
Using fonts is hard, that’s why most people who are not used to doing it and have no experience with it pick extreme fonts with obvious differences.