Absolutely there is a 'why'. Maybe not an experience, but as a psychology student we spend LOADS of time discussing why we act/feel/think the ways we do. However, in regards to sexuality, there is not an experiential factor. It is entirely biological, ie you are hardwired to like a certain gender (usually the opposite, and that's just a couple billion years of evolution talking, but of course that is not universally the case). However, what you desire in a partner of whichever gender you prefer CAN be influenced by experience, as can your level of attraction and desire to whatever it is you like. For instance, in the modern day Western world we idealize physical attractiveness as appearing physically fit (tall, muscular for guys and lean and flexible for girls, etc.). But go maybe 1000 years into the past in Medieval Europe, and you see the opposite. A lack of physical fitness (of course, not the point of obesity) indicated a privileged, and therefore superior life, and thus a more desirable partner. In fact, soldiers would wear combat armor with a 'gut' because it suggested to the enemy that they were far more privileged and wealthy (the physical and health implications of being heavy were not known yet).
Now, I myself am straight but don't feel incredibly strong feelings of desire unless I know her very well. I don't immediately have any attraction to someone even if they are good looking, unless I have a chance to interact directly. I think this is mostly because I am extremely picky about dating partners.
Now, I myself am straight but don't feel incredibly strong feelings of desire unless I know her very well. I don't immediately have any attraction to someone even if they are good looking, unless I have a chance to interact directly. I think this is mostly because I am extremely picky about dating partners.