Never used them, and yet I can unquestioningly agree. The way you had to number each line in increments of 10 so that you could insert a line 15 later in between lines 10 and 20 was, looking back at it, insane.
I can understand why they did it. In the era of no full-screen text editors, where you just typed each line one at a time into a REPL (not that I knew the term REPL at the time), and it stored the lines in the order of their lines numbers... well, that was the only way to edit your code. Made a mistake on line 20? Type a brand-new line 20 and it will replace the old line 20. Want to insert a line between lines 10 and 20? Type in line 15 and it will go and insert. So you could actually load your program, edit your code at the REPL, and save it.
But man, using an actual visual editor is so, so, SO much better than that system. I'm glad it's on the dust heap of programming history where it belongs. It was a decent option for the time when computers had 4K of RAM, but once it was actually possible to edit code in a full-screen editor, line numbers were no longer useful.