In Brazil (same place as the post author), some people do have many WhatsApp accounts. New number SIM cards cost equivalent to $3 dollars and dual SIM smartphones are very popular. Many people use these SIMs in a disposable way, changing them as telecoms change their prices.
That's true, but in my experience you have one at a time.
For south east asia it's normal to have one SIM for your local number and one SIM for your international number. Or just SIMs for different networks so that you can get free calls to friends who are the same network. But even then people usually have only one whatapp account at a time.
