> (i.e. say building a least squares model without using sklearn, etc.) It's 2023, when I read "build models from scratch" I think about training a model from

> (i.e. say building a least squares model without using sklearn, etc.) It's 2023, when I read "build models from scratch" I think about training a model from scratch and not using any pretrained models. For your definition, there's no good use case apart from learning, or making a custom implementation for something that doesn't exist in a library.