A confirm move button is needed for almost all games, real-time and turn-based, unless maybe if they are
extremely simple (Can't Stop), or have a built in mechanic that basically provides you with this functionality already (Jaipur).
If you have a tiny screen or Parkinson's disease, not having a confirm button can basically make it impossible to play a game. And literally anyone can drop a mouse or otherwise misclick and make an unintended move that loses a game. Why is this desirable? It could never happen on a table, yet it is inevitable on here if you play long enough. This should have been a design consideration, and done for all games right from the start.
The only 3 arguments I've ever seen against it are the following, and they don't hold water.
1. It takes too long for people to do their turn if they keep undoing - This is a dumb argument because people can take the same amount of time even without undo. If you want faster turns, use shorter timers.
2. I don't want to have to click confirm every turn - Solved with a player option to turn off/on confirm. Also, it only adds a single click per turn to a game at most, and some games wouldn't even have the one added click.
3. It lets players see the effect of their actions before deciding on a move - It would only let them see the one move, which doesn't seem to me like a huge forecasting advantage. This is also balanced by the fact that all players have the same option. And any advantage from this is further negated by letting the other players see all the moves before they are confirmed or undone (like Tash-Kalar). Obviously a player could never undo any move that revealed hidden information.
I can't imagine a reason why anyone would not want this feature.