Oh, and I'll add this too. ESPECIALLY for new players, prompted reactions are vital and how a DM would play Tabletop D&D. If I have a new player, they know nothing about what their characters can do. So, as the DM, I would prompt them during an enemy's turn. "Say. That goblin just ran by you. Want to use your Attack of Opportunity? It's your Reaction. You get 1 every turn."
New player then says, "HECK yeah! Why wouldn't I want to?"
If a new player is playing D&D and the DM doesn't prompt them, they have absolutely no clue they even have the option to hit an enemy who runs past them in melee, let alone using more complex reactions.
