Soap films are much more stable than films of water. Why? (Consider how surface tension reacts to stretching.)

Soap and water films are held together by their surface tensions.
The surface tension of soap solution is lesser than that of water. Water has larger surface tension. Due to this, water film cannot stay longer and collapse quickly.
The lower surface tension of the soap film is just enough to hold it for longer time than the water film. Thus, soap film is more stable than the water film.