Disarming an opponent in combat can be a good idea. Unless it leads to the opponent grabbing a replacement weapon that's better than the old one.
It's a good idea to have some handy potential improvised weapons lying around any place that a fight might break out. Imagine hitting a hook horror over the head with a handy stalagmite. Wading into a bar room brawl wielding a handy beer mug. Charging the evil wizard to try and smash them in the face with their own spellbook! Haha!
Commentary by memnarch (who has not seen the movie)
This is getting really serious. An extended fight and now a lightsaber gets drawn? It's actually rather hard to tell if Rey is trying to simply beat Luke or kill him. Not that metal staves can't be dangerous, but lightsabers cut through basically everything. This is like a wrestling fight where one of the wrestlers suddenly pulls a gun.
Will Luke actually die here? I hope not, but this is a very dangerous situation. Maybe his metal arm gets cut off and that's where the fight stops. Something about artificial limbs feels more acceptable to have removed; possibly because there's usually no risk of dying from shock or blood loss. Also possible is that Luke simply Force Pushes Rey back and then Force Pulls the lightsaber while she's stumbling back. Ooo! Or maybe we'll get to see the return of Force Arm-Wrestling if Rey can counter push! We haven't had that show up in the sequel trilogy yet; this would be a great time for that to happen if it's possible.
Transcript
Luke: I get up. I need something to parry with.
Luke: I Force Pull a lightning rod off a hut.
[SFX]: kzzack!
[SFX]: clack! {Rey attacks and Luke fends off the blow}
Rey: Fight back! You coward, fight back!
[SFX]: clack!
Luke: So! You belong to the Dark Lord.
[SFX]: clack! clack! clack!
Luke: I try to disarm. 20!
GM: The disarm is automatically successful.
Rey: I Force Pull my laser sword!
[SFX]: whooom! {Rey brandishes the sword at Luke}
Luke: Whoa! I step back!
GM: <roll> You stumble and fall.
Rey: Come on, get up and fight, you shivering junkyard!
Luke: Attacking your own flesh and blood with a laser sword?
Rey: I figured I’d take a swing at the family business!