Given that photography has never been more available to the masses, it’s quite legitimate to ask why anyone would pay a professional to take pictures.
There are many keen and competent amateurs and hobbyists out there creating some excellent work and I wouldn’t want to take anything away from their achievements.
What marks out the pro however is the amount of time they have to dedicate to their craft. A professional will have studied and have a sound background in aspects such as composition, lighting, post-production and presentation, not to mention an investment in equipment and facilities. A professional lives and breathes photography.
When photographing people in a formal situation, a career photographer will have patience and an ability to command whatever circumstances he or she is presented with. This is especially true of occasions such as weddings where you have to get it right first time, regardless of the environment. On other occasions, relaxed and informal, the photographer might have to blend into the background, being as unobtrusive as possible.
Overall, a professional photographer has to produce work that is of value. Work that people are prepared to pay for. To do this he or she has perform to a standard that stands out.