Everyone knows that women are attracted to guitar players but why? Most women who are attracted to guitar players don't know why themselves: they simply experience the attraction.
The simple answer to this question involves three parts. First, women are attracted to skill and guitar playing is a display of skill (and confidence). Second, women are attracted to men with social status (and leadership), and guitar playing is a display of social status. Third, women are attracted to men that other women are attracted to (pre-selection) and guitar players tend to have plenty of women vying for their affection.
Now, obviously, none of these explanations are unique to guitar players. It's just that guitar playing is our culture's easiest and most widely manifested way of attaining these three attributes with a single skill.
To understand this question more deeply, it's important to understand human nature and human motivation. Why are women attracted to displays of skill? To social status? To competition with other other women?
These traits are deeply ingrained in the animal hind-brain of female humans for evolutionary reasons. They have played a major role in the evolution and survival of our species. As mating strategies, they are literally written in our DNA - women do not choose to be attracted to certain types of men. They simply feel attraction.
At some point in our evolutionary history, it became ingrained (either through natural or sexual selection) for women to seek men who could display a socially useful skill. Having a skill was a sign that the man had more intellectual and physical resources to offer the woman than the average man. In the particular case of guitar playing, the skill is amplified by the pleasure of music and the perception of beauty.
The explanation for the value of social status is very similar. Social status is an indication of superiority, a measurement of collective intelligence. If the society to which a woman belongs marks the man with a stamp of approval, a lot of the filtering work has been done in identifying a man worth mating with.
Women have also developed the reproductive strategy of mating with men that other women show interest in. This is referred to as pre-selection - if other women are interested than it typically means the guy has high sexual value.
In closing, these explanations do not occur in the rational mind of women. They are not experienced as thoughts but as feelings of attraction. It is not as if the woman says to herself "this guitar player is attractive because he has a skill" or "this guitar player is attractive because other women are attracted to him" - rather, the attraction just happens, because of biological mechanisms that evolved for naturally identifying quality sexual mates.