I'm guessing this changed at some point, and either
1. those tutorials are outdated, or,
2. the people writing it for Angular 11 did not keep up?
But there's also this section: https://angular.io/guide/dependency-injection-providers
which clearly goes: "By configuring providers, you can make services available to the parts of your application that need them."
And now I'm more confused -- this goes over my head. 🙃
...and this section gives a bit more perspective. Looks like providers might be an advanced topic...?
But at least, it seems, you can see it's just one of three ways to provide a service. But in some situations, a service can be "provided" using *something else* other than Angular's service class... and I don't know when you'd do that, and how.
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