I noticed those comments as well and would make a slightly different point, which is that part of the reason it is good advice is that having a practical goal c

I noticed those comments as well and would make a slightly different point, which is that part of the reason it is good advice is that having a practical goal can be both motivating and directly helpful in the learning process. Motivating because you are more likely to finish a project that you want to use the result of. Directly helpful because it's easier to learn something when you see its utility at work.