The task Knuth was given was to illustrate his literate programming system (WEB) on the task given to him by Bentley, which meant writing a Pascal program "from the ground up", and (ideally) the program containing something of interest to read.
If instead of writing a full program as asked, he had given some cop-out like “actually, instead of writing this in WEB as you asked, I propose you just go to Bell Labs or some place where Unix is available, where it so happens that other people have written some programs like 'tr' and 'sort', then you can combine them in the following way”, that would have been an inappropriate reply, hardly worth publishing in the CACM column. (McIlroy, as reviewer, had the freedom to spend a section of his review advertising Unix and his invention of Unix pipelines, then not yet as well-known to the general CACM reader.)
So while of course shell one-liners are faster to bang out for a one-off use-case, they obviously cannot accomplish the task that was given (of demonstrating WEB). (BTW, I don't want to too much repeat the earlier discussion, but see https://codegolf.stackexchange.com/questions/188133/bentleys... — on that input, the best trie-based approach is 8x faster than awk and about 200x faster than the tr-sort script.)
If instead of writing a full program as asked, he had given some cop-out like “actually, instead of writing this in WEB as you asked, I propose you just go to Bell Labs or some place where Unix is available, where it so happens that other people have written some programs like 'tr' and 'sort', then you can combine them in the following way”, that would have been an inappropriate reply, hardly worth publishing in the CACM column. (McIlroy, as reviewer, had the freedom to spend a section of his review advertising Unix and his invention of Unix pipelines, then not yet as well-known to the general CACM reader.)
So while of course shell one-liners are faster to bang out for a one-off use-case, they obviously cannot accomplish the task that was given (of demonstrating WEB). (BTW, I don't want to too much repeat the earlier discussion, but see https://codegolf.stackexchange.com/questions/188133/bentleys... — on that input, the best trie-based approach is 8x faster than awk and about 200x faster than the tr-sort script.)