You do. All of your friends do too. It's impossible not to.
Accents develop based on the voices you hear while growing up. You will naturally start to mimic the way those people accent how they speak the words they use as well as their cadence, camber, pitch, etc. etc. etc..
I have a midwestern U.S.A. accent, which a great deal of people within the U.S. don't seem to consider an accent at all because it's basically the accent of broadcasting and considered "normal". This is still a f***ing accent.
Why do other people not speak like, whatever you seem to think is not having an accent? Cause they speak how they grew up speaking, or maybe english is not their first language [and thus they are likely smarter than you since they know more than the 1 language you know. ].
Take, people from Japan. It has 101 different phonetic sounds [don't quote me on that, been a while]. None of these make the same sound of the letter L. The closest thing is the letter R. Which is why they often substitute L with R when speaking english, because they aren't used to making that noise. Aaaannnd I'm pretty sure if you attempted to speak French you'd be throw for a loop with a lot of the sounds in their language. Or the ! sound within some african languages. Why? Because it's f***in' hard to master a language you didn't grow up speaking.
Also, you don't strike me as terribly smart. You're not even aware you speak with an accent.