Mostly for business. Maybe some people are comfortable to Whatsapp you, but it's inappropriate for a lot of situations.

Also, in a lot of places you need a local number to get things done. Like when making reservations at restaurants or you leave your number in the POS to have them text when a table is ready, etc.

As it is, I have a dual SIM Android phone as well as an iPhone and have 3 postpaid plans in different places. Massive pain.