There is a new world of their product, and even though it's 2018, they're not in it. It might feel like Spotify has won, Netflix has won, and so on, but in other verticals, subscriptions still aren't the norm.
Remember when Dollar Shave Club started selling razors by the month and got bought for a billion dollars? P&G needed to find a way to transition to subscriptions, and they paid up for it.
The subscription economy is a real trend, and it's not something you can just convert to overnight if you have a business that's a going concern. You have to figure out how to put out some new offerings, and the way people pay for these new subscriptions have to work with your existing business processes.
Zuora sells to those companies. Companies that want to sell subscriptions, but can't throw the baby out with the bathwater. They want to work with a company that understands that subscriptions are the new important thing, but not the only thing.