Why ? The Empire believed that the Death Star was impregnable. They did not consider small fighters a threat and tried to shoot them down. They only tractor beamed the Millenium Falcon because they were looking for the stolen Death Star plans.
They were also unaware of the weakness the X Wings and Y Wings and A Wings were sent to exploit.
Do you also really think that The Empire would go "oh look, the enemy, bring them in gently lads ?"
