I understand that you want to be on the sidelines. I understand you want pictures of your daughter playing soccer. I understand that you want to justify purchasing $3000 worth of camera equipment to your wife. But understand this: if you want to act like a professional, you need to behave like a professional.
There are certain rules that you must adhere to in order to be on the sidelines. The lines on the field are there for the safety of the players, coaches and referees. When you cross over that line you are directly in the playable area. Referees run through this area. Players will dive into this area to save the ball from going out of bounds. This is not a safe place to be.
And lastly, you have to wear shoes on the sidelines. I’m not sure what gave you the idea that this acceptable but it is not. Please dress accordingly.