1) People select a watch because of the way it looks at a glance. Here is a simple test. Buy a new band for your watch, different from the band you have been wearing. Ask people how they like your new watch. Many people will insist that it is new, even if they see you and your watch often. They notice the band, not the watch itself.
2) People buy a watch to impress others. This is why there are so many watches that "look just like" other brands. Whether they are buying a knockoff or paying full retail for a watch that costs more than many cars, it is designed to do the same thing- to create the impression that this is a person of wealth and taste. Advertising has worked once again.
3) People buy a watch to augment some notion of self image, sometimes based entirely on fantasy. Think of the racecar and diving models that have never been in any body of water deeper than a bathtub or timed anything at all. How does your watch make your car go faster? Does a "combat model" watch protect its wearer in the battles of everyday life? Like with clogged sinks?
4) People buy a watch as a piece of jewelry. Why else would it matter whether the case is made of gold or steel (or plastic)? Have you ever noticed the difference in price between a gold watch and its stainless steel model? How much gold can you buy with that difference? How much gold is actually used in the watch?
5) People buy or receive a watch as a gift, in which case they have no choice at all, except whether or not to accept it.
6) People buy a watch because it is fun to play with- think of watches with display backs, stopwatch features, glow-in-the-dark, elaborate mechanisms, etc. but see below.
7) People buy a watch because it has a brand name they know and enjoy, whether it is a famous watch brand or the name of a designer whose other products they buy. Why else would anyone have a Nautica or Anne Klein watch?
8) People sometimes buy a watch to conform to a trend or fashion- look at the rise of really BIG watches, for example, or the popularity (and subsequent drop off) of Swatch.
9) People sometimes buy a watch from convenience. They need to be able to tell time and the one they buy is the first one they get their hands on, or more accurately, get onto their hands.
10) People often will buy a watch based on price. They may buy an inexpensive watch because it tells time cheaply, or they may buy a more expensive one at a bargain price. Some people will buy a notoriously expensive one simply because it is- see #2, #3, and #5 above.