I am living in spain and I never used whatsapp professionally. I've had a few messages sent by medical clinics to confirm appointment, delivery workers to drop a package or some others pros but if you don't have whatsapp they just call you anyway so it is not necessary.

Most people in Spain still rely and prefer voice calls than messages anyway. I believe half the country must still be illiterate as they manage to send voice message but struggle to send written messages on whatsapp.

On a personal level you lose a bit of information when you don't have whatsapp. For example I didn't join the whatsapp group of my dance class and I am often unaware of stuff they mention on it but that doesn't prevent me to attend said classes.