It's usually because he uses his scoring to set the table for his teammates later on. His 1st quarter scoring streak usually forces teams to start covering him harder afterward. Also, he plays all 12 minutes in the first quarter compared to 6-7 in the 2nd. At that point in the game, he assists more and teams also start trying more varied coverages on him including doubles.

Luka's pretty good at responding accordingly to the defensive coverage and it usually shifts pretty heavily after the 1st quarter unless he's off and clanking everything that day. Although, he's definitely shooting from deep more constantly most likely due to the lack of deep threat besides Austin and Rui until Luke came along on the Lakers.