Because polling on phones these days must include mobile phones to be accurate, which is every expensive because computerized dialers are illegal for mobile numbers. To poll mobile phones, you must have humans manually dial each number.
Polling is a major expense for campaigns. Anything that gets that cost down is a strategic advantage. That said, online polling has a LONG way to go before it is as accurate and trusted as phone polls.
Polling is a major expense for campaigns. Anything that gets that cost down is a strategic advantage. That said, online polling has a LONG way to go before it is as accurate and trusted as phone polls.