Because insurance companies don’t have customers who call constantly to complain about not getting loot from a boss or not being able to fly on day one of an xpac or how she can’t mog the cute gray item from vanilla, times millions.
Insurance companies are all about customer service since they’re paid tons of premiums in the event of something happening (accidents/death/disaster). Those companies don’t have millions of customers logging into their systems to play the insurance video game.
Blizzard is about developing video games. Customer service is incidental.
That’s why there’s no phone support for WoW.