Maybe they're finally capitalizing on all their locked-in users.
Ex: see all the Google Photos competitors who are doing the "I told you so" roadshow when they announced the end of unlimited storage for free. Other apps couldn't compete and/or died out, and so with market share in hand Google could "raise" prices.
Further, Google doesn't hide that they want to grow "services" revenue, and had mentioned it in previous investor calls. I'm guessing they're seeing the success Tim Cook has had with diversifying revenue and growing services like crazy, and now they want to leverage that channel for growth.