As someone else who has built streaming things, HTTP range requests aren't enough all of the time.

Quite a number of older Android clients, like TVs, cheap phones, etc. don't have an up-to-date browser on them, and they will make the first range-request correctly (with a byte range that reflects the browser knows the full content-length, etc)...

But you'll have to build your own scheduling system to pull in further requests, which is painful, clumsy and doesn't always work.