It’s tempting for declarer to draw all the trumps when on lead, but is this always the best approach?
Imagine this is declarer’s combined holding (with dummy) in trumps:
Once declarer gets on lead, s/he will usually play A & K hoping that trumps have broken 2-2 and that two rounds will draw all the outstanding trumps.
Statistically, it is more likely that there will be a 3-1 split. Playing K & A will then draw 3 of the outstanding trumps, leaving the Q still with the opponents.
Should you play a third round of trumps to draw the outstanding one if it’s a winner? Usually, it will be better to switch to playing on the side suits. This leaves declarer with the possibility of using the 2 trumps in dummy for ruffing or perhaps for setting up a suit to discard losers.
At some stage the opponents will use their winning trump, but leaving it outstanding may allow declarer to make better use of their remaining trumps.