GX.Sigma
Adventurer
Ok, it's not about the standard wizard. He's holding his staff in one hand, and casting with the other which is holding nothing. Easy peasy.
But say you are a "gish" - a fighting caster of some kind... like let's say an eldrich knight. Now if you are fighting with a great weapon, still no problem - your left hand holds on to the halberd while you cast with the right. Once you've done casting, your right hand re-grasps the halberd.
BUT. If you are fighting with a shield and sword, or two swords, then it gets complicated fast. You can put away or draw "for free" as part of your attack or spellcasting, but *not both*. And more importantly, you can't do that as part of a bonus action or reaction. So you can cast/attack on your action and end your action with drawing/sheathing your sword... leaving yourself with a weapon in hand. But then if you have a reaction - you can cast, or you can attack, but if you "chose wrong" (ie you still have your sword in hand but you really need to cast shield) you are kinda screwed.
And why is this a problem for you? Is it because it incentivizes using two-handed weapons?