In many places WhatsApp is the defacto standard unfortunately.....
If its not that its something like Viber, or badoo or telegram or some other nightmare service...
If you have kids there is also not really getting away from it. Friends of mine have never had Facebook accounts until they had kids because the local football team or boyscout or whatever only uses Facebook to communicate...
I agree you can live your life comfortably without meta services, but sometimes, like in the example above, you dont have any alternatives....
You can't keep harassing other parents to forward you messages or ask the team to print any messages specifically for you. Not having a Facebook account just gets "its easy to create" responses rather than "completely understandable, here's our private matrix server to stay in the loop".
Not to mention that if you want to type it in somewhere ( like your car for a Spotify account or whatever ) a passphrase like
Hunter7-Tower-Ballsy9
is easier to type than some random gibberish with special chars.