Pain in the Backside
A good saddle is important for long rides, especially if you ride many times a week as this can take it's toll on your backside if you aren't comfortable in the saddle.
A quality saddle doesn't have to be wide with plenty of padding, in many cases this is actually more uncomfortable for many regular cyclists. Contrary to popular belief, it's not about the amount on padding in a saddle, it's about the support it gives you.
Crucial Supporting Role
The saddle should be supportive under your sit bones and wide enough to accommodate these only, it doesn't need to support your glutes or any other part of your anatomy.
Brands like Fizik have made their reputation on creating saddles that are extremely comfortable but also really lightweight, perfect for racers or riders who are conscious about the weight of their machine. Especially when combined with a lightweight seatpost to really make some weight savings.