Do you think tickling a teenager you know is weird compared to a small child you know?

Some of you may recognize this question, I just wanted to see if I get any more responses. I asked a question before on whether fathers these days ever tickle their teenage sons, around 13 - 15 years old more so. While I didn't get a lot of answers, one that I got said it sounded perverted to them. And I remember reading a comment somewhere else that said 15 is too old to be tickled. But here's my question, more or less. Why is it that it's perfectly normal to tickle a small child, when that child can't often defend themselves. I have seen friends hold their small children down sometimes and tickle them, and sometimes the child is too young to even say no. So why is it not perverted to tickle a small child who may not be able to defend themselves, yet it's weird to tickle an older child who can defend themselves and say no when they want/need to? I don't understand this. Do y'all think it's weird to tickle a 14 year old boy (who let's say you know quite well), but yet it's not weird to tickle a 4 year old who can barely defend himself?