First, if they don't increase HP, the fight will be too easy. Games should primarily be fun. If players miss too often, it can be frustrating for them. It problem with turn-based games which you can't easly fix by adding extra enemies because fights will be to long.
"Missing is not fun" - that just feels very much like a problem of modern gaming to me. And damn, I am not even that old. Gamers are used to playing with skinnerboxes of constant gratification. So the new motto for games is: "Ohhohh, better never do something that could be misunderstood/is not working immediately, or someone will complain on the steam forums".
To this day, one of my favorite games of all time is Morrowind. I got it and tried it. Could not hit a stupid crab right in front of me and quit. Like the child that I was at the time. Then I read online, how it actually works, understood what I did wrong and became better. And holy shit. This game offers so much freedom in probably the greatest sandbox games of all time, that no game since could replicate. And why? Because Oblivion and Skyrim did so much better. It is the "I clicked on it, it must hit"-Crowd. If the skinnerbox is not giving out gratification, its not working right, and so many people got used to it. From an economical standpoint: I get it. But game design really got cowardly.
