Why do you think Dallas helps the two boys escape and does not encourage them to go the police in The Outsiders?

Dally did not recommend that Pony and Johnny go to the police because the greasers do not trust the police.

Pony goes to great lengths to describe the difference between Socs and greasers.  The Socs are rich kids, and they have everything handed to them.  They get all the breaks.  When Socs get into trouble, no one pays much attention.  The greasers have run-ins with the law all the time.

We're poorer than the Socs...

Dally did not recommend that Pony and Johnny go to the police because the greasers do not trust the police.

Pony goes to great lengths to describe the difference between Socs and greasers.  The Socs are rich kids, and they have everything handed to them.  They get all the breaks.  When Socs get into trouble, no one pays much attention.  The greasers have run-ins with the law all the time.

We're poorer than the Socs and the middle class. I reckon we're wilder, too. Not like the Socs, who jump greasers and wreck houses and throw beer blasts for kicks, and get editorials in the paper for being a public disgrace one day and an asset to society the next. (Ch. 1)

Johnny and Pony are considered juvenile delinquents.  That is just society’s impression of the greaser.  When Bob attacks them and they fight back, they know that the blame will be put on them and not Bob.  Bob was drunk and he was the aggressor, but he was rich and they are poor.  There is no way the cops will give them a fair shake.

Dally knows this.  Johnny and Pony go to him after Johnny kills Bob because he has had many run-ins with the law and knows what to do.  He takes charge immediately, helping Johnny and Pony skip town.

"Hop the three-fifteen freight to Windrixville," Dally instructed. "There's an old abandoned church on top of Jay Mountain. There's a pump in back so don't worry about water. Buy a week's supply of food as soon as you get there--- this morning, before the story gets out, and then don't so much as stick your noses out the door…” (Ch. 4)

It is a good plan.  Dally was going to meet with them as soon as he could.  The problem was that a group of kids showed up and the church caught fire.  Dally, Pony, and Johnny tried to rescue them.  The paper praised them as juvenile delinquents turned heroes.  They were all hurt, but Johnny was hurt the most seriously and never did recover.