By making use of Blockchain technology for everything, global control will be enforced as it's much easier to track every single transaction made worldwide. Those transactions will not only involve money, but also transfer of ownership, certificates of birth, driver's license, and other services within the global Blockchain system. This may sound crazy, but if you look at the current situation where many Banks and governments have become interested in the technology, it shows us that it will be implemented in every area worldwide within the not-so-distant future.
You don't need blockchain to do any of that, and if we are talking about centralized entities, blockchain doesn't make any difference at all. Imagine if you stored files on your computer on a private blockchain, what would it give to you? You could use it to notice that some files are missing, but there a lot of other and more efficient ways to do it. Same with governments, the real reason why they show interest is because the got caught in hype just like retail investors do - government officials aren't some brilliant people who are experts in everything, and they can be misled too.