by sigmazero13
By guess is that it's partly due to abilities like the Knight; if you drew a card mid-battle, and then played it, it could be a bit too strong for Daqan.There were possibly also some issues with Strategize orders where you draw cards, and then want to play one immediately.
It does take a little getting used to the rule, but I think it does help take the edge off some of the random luck that the tactics cards could bring by making you wait to use them instead of being allowed to draw them and use them instantly.