A college professor I had many years ago once answered this exact question with the Ice Cream Store analogy...
Four friends pass an ice cream store everyday. They have never had ice cream. One by one they decide to try ice cream.
Person A looks at the choices, and chooses chocolate. They love chocolate. To them it is the perfect flavor. Whenever they want ice cream they choose chocolate. They see other people enjoying the other flavors, but they don't care because they love chocolate and they have chocolate for the rest of their life.
Person B looks at the choices and chooses peach. They love peach. For years they eat peach. They notice people really enjoying other flavors and they wonder what they taste like. Peach has become boring for them and they eat it out of habit. They are afraid to try other flavors. Sometimes they don't eat ice cream for long periods of time, but when they do it is peach because peach is always there and htey know what it will taste like.
Person C decides they are going to try lots of flavors. They like some, dislike others. They find that they keep coming back to vanilla, so they decide to eat vanilla for the rest of their life.
Person D also decides to try all the flavors, but can't decide on a favorite. They keep trying all the flavors and really look forward to new flavors. This is how they eat ice cream for the rest of their life.
It comes down to there are lots of things that make up a person (experience, family, age, religion, etc) and they all influence how they choose their ice cream. The most important thing is deciding how YOU will eat ice fream.
Everybody is different. There is no simple answer of why. Human beings are way too complex, so trying to understand every point of view on any given subject will drive you nuts.