You may have heard the term "a photographer's eye". In this day & age of digital photography this term has never mean't more than it does today. Professional cameras have novice photographers, even hobbyists, shooting weddings and giving "great deals". Couples are often blindsided by these deals and unfortunately don't realize it until receiving the final product. Understanding what makes a great photo and seeing that consistency throughout a photographer's wedding portfolio is vital to ensuring a great package of photos.
A great photographer sees and frames moments of time that others often never notice. He/she always expects the unexpected. Some of the best photographs happens in the fraction of a second and if the photographer is not genuinely working in the best interest of the couple these often go missed. No matter the venue, a skilled photographer can create great pictures and easily adjusts under any circumstances (inclement weather, shortage of time, last minute schedule changes, etc...) without it becoming problematic for the couple. It's important for a couple to see hundreds of photographs, covering all aspects of the wedding day as it relates to their wedding, and making sure they see artistic consistency throughout the work. A photographer may have strong outside work but the quality of their work drops off considerably in their indoor work due to the lack of technical skill when it comes to shooting in venues with lots of windows & mirrors (most venues).
Fortunately for couples, "the proof is in the pudding". If a photographer's website only displays approximately 25 photos then this is not a good representation of the overall package of photos you'll receive from your wedding day.