In the old days, streaming videos was a pretty hard thing to do. These days, we have relatively simple video controls in modern browsers, and each of them tailor the experience to the device you're using. This is a good thing. The problem is that there are likely some of you that don't have a more modern browser that supports the latest (and a few years old now) HTML standard. And then there are platforms (ahem, Apple ...) that removed support for any of the older ways of getting video to you. Given the security issues and general misery of the old software (generally, running "Flash"), this is also a good thing, because it's forcing content providers to upgrade.
Why the missive? Because we only support HTML5 right now. That means older browsers (like Microsoft Internet Explorer 9 and earlier) won't work well or at all. You should probably upgrade if you're using that anyways. And on Windows, there are these new packages called "portable" packages, for which you don't need to be administrator to install, so you can install it on your work or school computer, a USB thumb drive, or whatever, and it'll work.
Some helpful links: