For me it is because I have been lucky enough to meet some great people these past years, and some of them are so dedicated to the hobby. Every item they find tells a different story and makes you ask questions.
Who lost this? Where was it made? I wonder what is cost? Did the person who lost it get into trouble?
What other questions do you ask?
For me it's the 'time-travelling' aspect. The more finds I make from a field, the more the story of what happened there comes to life. How wealthy the folk were, what they doing on the site, and for how long. You then set the scene against the backdrop of history, placing their lives against the the events of the day. Going back to the land every year after harvest, and you feel a kind of welcome, because now your wanderings are part of the big picture.