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PHB p141, footnote 4 to Table 8-2. "Combined with a regular move".
So, for example, if you Charge, you can't draw without the feat - it's a full round action, and you aren't making a regular move.
If you throw multiple daggers, you need the Quick Draw feat.
If you're someone who regularly switches between reach weapon and (close) melee weapon, or melee weapon and ranged weapon, the Quick Draw feat is useful.