I think you are:
I loiter around all day,
Doesn't really do anything for you
Until you kick me out for the week,
You might trim your facial hair once a week
You may invite me back in until I've evened out.
I will always be back to linger your way,
You can even it out, but then it grows back and gets in the way.
Gruff, big, small and chic,
Those are all forms of me, no doubt!
Different styles of facial hair.
Near a parenthesis like thing, I lay.
Your mouth. Has a slight curve to it and it opens and closes.
And cutting edge technology, a nemesis name it reek(s).
Cutting edge technology is a pun, not sure about the second part.
Lastly, I just sit here waiting for every scrap that doesn't find its route.
Food crumbs could get stuck in your beard/mustache if they miss your mouth.
I "mustache" you this