Smartphones have kept on using the same old 16 GB of storage at the high-end with an option for 32 GB for $100 more, and it seems long overdue that OEM's start offering more storage for the same price as before, and also higher storage options, as the storage base line increases.
Why are we starting to see this now? Because prices for smartphone components drop by 30 percent per year, putting the price of storage even this year at $60 for 128 GB, which means OEM's could offer 64 GB for an extra $50 (with a little profit for themselves), and 128 GB for an extra $100. Compare that to how most of them charge $100 for only 32 GB more, which is 4x less than they could offer.
In the past few years, I wasn't so concerned OEM's increasing storage space, because there were other components that had to be improved first (such as moving to 720p resolutions, then 1080p, or using better cameras and so on). But 16 GB, and even 32 GB is starting to seem too low these days when some OEM's (like Google/Motorola) don't even include microSD cards with their phones, and cameras are starting to use higher resolutions for both stills and videos, which means much less fits in the same space.
Then there are also the apps which have continued to increase in size, and the operating systems themselves, which can take from ~2 GB installed with all the apps, to 8 GB or more (like Samsung's Touchwiz/Nature UX).
Put all of these together, combined with the much lower cost of flash storage these days compared to a few years ago, and you can easily see why all OEM's need to start offering at least 32 GB by default to all of their devices from mid-range to high-end (possibly even offering 64 GB by default for flagships, with 128 GB options), in 2014.