Why are the lessons not up to date?

Why are the lessons on the home page not up to date? Setting up the dev environment did not go as per the lesson (it refers to the installer which has subsequently been removed), and now I’m stuck on the Working with Multiple Templates lesson regarding namespaces (the lesson uses them but my version of SilverStripe does not support them and throws an error when I try and add namespaces to the PHP files).

If you post some details about the errors you’re receiving, we can probably help you to get going again.

If you’re using Silverstripe 4, then it will support namespacing, so hopefully it’s just a simple config issue.

The bulk of the lessons are still correct, but as you’ve found, the software has moved on a little in some areas and the lessons haven’t caught up yet.

To answer the question in the title: resourcing. Silverstripe doesn’t have infinite resources, so the lessons have taken a bit of a back seat.
That said, they are open source (click the “Code repository” link on the page you linked to), so anyone can create pull requests to update them.