The rules about having a hand free for casting are often misinterpreted, leading people to think that video games are forgetting something, or to video games themselves being overly harsh on the interpretation.
Here's what you need to remember:
Does the spell have a somatic component (s)? If not, then you don't need any hands at all anyway.
Is one of your hands at least nominally free? If so, then you're fine to cast somatic components - this means that someone using a bow, or wielding a two-handed sword is perfectly free to use their action to cast a spell with a somatic component, because two-handed weapons and bows etc., only require you to have both hands on the weapon to use them, not simply to hold them, and taking one hand off the weapon to make your somatic gestures for your action is perfectly within the rules.
The hand that is being used for material components (holding your arcane focus or manipulating your component pouch, etc.) is Also a perfectly acceptable hand to use to make your somatic components simultaneously.
This is still an issue for dual-wielders of course, but outside of that, for the most part and in most cases, this means that most characters interested in casting spells are naturally going to be able to have a hand free to do so... So a video game that disregards book-keeping this isn't really making Toooo much of a rule bend, most of the time.
