Extension boilerplate not using CSS in developer rig (or otherwise)

I’m fine with that being the issue, I’m trying to narrow down why.
That I understand, I should be able to download the boilerplate, get it served and running (it has the auth and twitch includes itself) and start making changes, no?

I have noticed on reinstalling the rig and downloading a fresh boilerplate that it starts with the css stripped, the ‘App-light’ class gets assigned by the boilerplate, but there are no CSS properties attached, although the boilerplate specifies different text colors.
This is without me having touched any of the code.