Thunderbolt is great, but it really is only needed for high-bandwidth applications. Couple that with the high cost of Thunderbolt peripherals and I can see why it hasn't gone mainstream.
I use Thunderbolt for my RAID 5 array. (20 TB, spinning disk, 4-drive array) and it is smoking fast. Every time I access it for large files, it still amazes me even after 2 years of heavy use. But when it comes to a single drive, Thunderbolt is not worth it since USB 3/3.1 can already transfer the data faster than the drive can read/write so it is a moot point. Why spend an additional $50-$60 to get Thunderbolt when it makes zero difference in performance for a single drive? (Not directing this at one person, just a discussion point for all.)
Thunderbolt is amazing when you need it. Unfortunately, we are still somewhat limited in the number of real-world situations that require it. However, this is rapidly changing as people begin to drive high-resolution displays and especially as they daisy-chain additional peripherals onto those displays.