Awk is one of my favourite software tool language, but some of these one-liner scripts can be done better with sed and tr.

Yep, some of them can be done much better with sed and tr.

The goal of this article, however, was not to illustrate the best practices but to document all Awk one-liners in awk1line.txt file.

It left me wondering why people think that file is so great.

Because books do not teach writing concise scripts, they would expand on multi-line functions, etc.