I was reading a closed question that proposed different rulings on Disarm, and it leads me to ask a proper question about the disarming abilities in 5th Edition. The Battle Master maneuver Disarming Strike is among the best example, but in all instances; when you succeed at disarming someone the weapon simply drops to the target's feet.
Is this redundant in that the same creature can then JUST bend over and pick it up again when it's their turn, as a free object interaction, that costs them nothing in the grand scheme of the combat action economy? Or is there something I am missing in how this can be effective in combat as opposed to just a slight annoyance?
I understand it MIGHT potentially rob them of opportunity or reaction attacks until they can pick up the weapon, provided it's the only weapon they have to make such attacks with; but there must be more to it, yes?
Best Answer
Grabbing it is easy but...
It is easy to grab it back on their next turn, but you could also grab the weapon as your free object interaction (maybe even on the turn you disarm them!), assuming you have a hand free.
Separate them from it
You could also knock them away with another action (like bull rush) or a spell (like Thunderwave) if you can't grab it, forcing them to waste movement getting back to the weapon (or at least eating an opportunity attack from you while they try).
Denying battlefield control
As you also state, it can easily deny them any opportunity attacks (most things that use weapons probably don't have excellent unarmed skills). That actually is quite good; there is a feat that does a very similar thing, but only for you. This could work for all of your allies until the target's next turn.
Denying features or abilities
Finally, there are some features that require a weapon, like the Fighter's parry ability, as well as some monsters' parry ability. Disarming a creature of a magic weapon might also prevent them from using its abilities/bonuses until they pick it up again (like the magical sword that allows you to turn attack bonus into an AC bonus).