Are you really that surprised?
Netflix is increasing the prices for its service. Granted the most popular package is only going to be $1 more. But you can probably expect it to happen again, eventually.
As for their Standard, single screen low resolution plan, that’s still $7.99. But for the popular High Definition, two screen plan that was $9.99? That will now be $10.99. The 4K package will be bumped up from $11.99 to $13.99, but who really needs 4K right now anyway?
As for why, well, that’s just Netflix’s strategy. They adjust their prices according to the market, and there’s just more on offer now. At least it’s still cheaper than a lot of the “Premium” services like HBO and Starz.