From a former PE teacher ( I now teach technology education):
I don't know where you are, but Ive never met a PE teacher in my area that meets your description of one. Everyone thinks schools should teach more life skills, and PE does exactly that. So much of our country is overweight/obese. From the time students are in Kindergarten-12th grade, PE introduces them to all sorts of sports, activities, and recreation opportunities. It gives young people a base working knowledge of coordination, strength, and understanding of sports and activities. If they are introduced to volleyball at a young age and have exposure to it until they graduate, when they become adults and a friend wants them to join their intramural volleyball team, they may think "Hey, i know how the game is played, and I was OK at it in PE, I'll play" Instead of, "Ive never played volleyball ever, I dont know how to play, no thanks".
Developing the skills in school during PE playing games, sports, and activities leads to confidence to pursue a non sedentary lifestyle when you become an adult because you are more confident in your ability. The first person responsible (outside of parents) in creating this motivation is probably a child's PE instructor. Many PE teachers here create a wonderful atmosphere where kids thrive in activities, they want to get better, and they want to participate.