The Philistines seemed to prefer enslavement as shown in
1 Samuel 17:
8 And Goliath stood and shouted to the ranks of Israel, “Why do you come out and array yourselves for battle? Am I not a Philistine, and are you not servants of Saul? Choose one of your men and have him come down against me. 9If he is able to fight me and kill me, then we will be your servants. But if I prevail against him and kill him, then you shall be our servants and labor for us.”
The Philistines wanted Samson alive.
Judges 16:21 Then the Philistines seized him, gouged out his eyes
They punished him.
and took him down to Gaza. Binding him with bronze shackles, they set him to grinding grain in the prison.
They made him work.
25While they were in high spirits, they shouted, “Bring out Samson to entertain us.” So they called Samson out of the prison, and he performed for them.
They wanted him for entertainment.
Why didn't the Philistines killed Samson while he was sleeping?
They didn't want him to just die easy. This all worked out for the purposes of God.
29And Samson reached out for the two central pillars supporting the temple. Bracing himself against them with his right hand on one pillar and his left hand on the other, 30Samson said, “Let me die with the Philistines.”
Then he pushed with all his might, and the temple fell on the lords and all the people in it. So in his death he killed more than he had killed in his life.
The Philistines wanted Samson alive to entertain them but God had another plan.