Nothing shakes up wrestling's status quo like a well-executed turn.
Whether it comes out of the blue or at the end of a long-term program, turning face or heel can send a wrestler's career stratospheric, launching them to heights that wouldn't have been possible otherwise. Going heel saved The Rock's career in 1997, and while turning isn't always this transformational, history is littered with similar examples.
Very few wrestlers excel on both sides of the alignment scale, though. Depending on their character traits, attributes, and history, it's extremely easy for a wrestler to get typecast as one or the other, leading to the perception that they should remain stuck in their current role forever.
This is a shame, as we never truly know how a wrestler will fare as the opposite alignment until it's put into practice. Some of the sport's most memorable face/heel turns have come from situations where the performer's new role was seemingly at odds with their strengths and weaknesses, but it's a big risk, and success stories are rare.
This only makes the tales within all the more remarkable, as each prospered when turning should've been a disaster...