Why is there a DRAW market for the 90 minute market in a cup game, when there has to be a winner declared?
There is a draw market because the draw can still be a result at the end of full time (90 minutes). You are betting on what the result will be at the end of full time, not on who advances to the next round or lifts the cup.
Should the result be a draw, say 1-1 at the end of full time (including injury time), then this will be the winning option. What happens in Extra Time or Penalties, will not affect this result. Read here for more info.
If you wish to bet on who will advance to the next round from this game, or who will win the cup, then the right market to bet on is either “To Lift the Cup” or “To Qualify For Next Round.” This will not have the draw option.