Stiles always knew that he couldn't stay pack forever, definitely with the amount of secrets that he has weighing his back. He almost wanted to believe that he could, that he would always have that group to lean on; however they never needed him, and surely he never needed them. After all stiles is Thomas, and Thomas has his own family.
Of course his family wasn't the traditional type, they all loved each other in different ways; all very different types of people. However the differences strengthened when WCKD pulled the plug stopping their abilities from showing. After all WCKD isn't good.