As someone who can't make it through a pedicure without almost reflexively kicking the aesthetician because my feet are so damn ticklish, I was always extremely confused at how other people could just sit there calmly, not batting an eyelash. Now, I know I can't be the only one here so I decided to actually look into why some people are so much more ticklish than others.
As it turns out, there are a few different theories when it comes to figuring out why we're ticklish, but the basics of what it boils down to is evolutionary advantage. The areas that are most sensitive to tickling (like your stomach, neck, feet, etc.) are generally areas that are the most vulnerable, and therefore need protection from potential attacks. The more sensitive you are, the more prepared you'll be.
We never would have seen this coming, but tickling is also thought to encourage the development of combat skills - another evolutionary advantage. I guess it makes sense since if you get tickled enough, you eventually figure out a way to defend yourself against it.
As for why you feel it more, like people who are super-smellers or super-tasters, some people just have a heightened sense of touch and are affected by tickling much more than the average person. Also the younger you are, the more sensitive you are to tickling, so you can just blame it on your youthfulness.