Yes, its called business.
You incentivize (aka manipulate) consumers to pay or engage with your products.
Every company before Blizzard has done it, Blizzard has been doing it since their inception, every company after Blizzard will continue doing it.
Yes, it sucks.
But the issue lies in capitalism itself rather than Blizzard as an individual company, Blizzard is just doing exactly what it was created for to do: make profit.