Could have been a matter of older age but I remember the same happened to data input operators at work that switched from DOS applications to mouse based programs. Productivity plummeted.
Most people who used WS loved it, and they only traded it under duress for say WordPerfect.
I still have hundreds of files in WS format and from time to time I've imported some into MS Word in the days when it had a WS importer but now I no longer bother. The reason is that I now have WordStar 7 running under emulation on Windows 7.
It's strangely familiar to be editing with WordStar on Windows these days but it still has its advantages. If one uses dozens of different programs like I do, one finds it's often difficult to remember where some particular feature is in the menus from one program to another. For instance, I use MS Word to about the same extent as I do LibreOffice and I'm forever annoyed that they don't have the same menu/command structure as it wastes time constantly switching one's mind around.
This is particularly annoying when simultaneously using Windows machines side by side with Linux ones. On Windows one's using Office, and on Linux LibreOffice.
Using a command line editor like WordStar solves this because one automatically knows where all the Ctrl keys are.
Sometimes when I'm trying to get thoughts into text quickly I'll bash them out in WordStar then if necessary I'll pretty them up in Office or LibO.
Your mother was absolutely right, command line wordprocessors are great for quick entry and when you don't want your train of thought distracted by mucking about with formatting, etc.
WordStar was wonderfully logical this way.
Incidentally, I remember years ago in the 1980s at a software trade show where MicroPro was exhibiting its new WordStar 2000, talking - almost arguing - with Seymour Rubenstein (the owner of WS), that the new, supposedly simpler but quite different, command structure in WordStar 2000 wouldn't take off and be popular, as all old WS users wouldn't want to relearn new commands for ones that were perfectly OK and that it would have to compete with established WordPerfect and the new kid on the block MS Word. Turned out that I was right, WS 2000 died long before its older sibling did. This is a classic example of how not to tamper with or upgrade a perfectly good product.
Just like that Polish mechanic who was still in the 21st Century using his custom coded C64 program for wheel balancing, how many of us who pine for the good old days still wish to live in them? I argue we still in fact have that choice - don't we?