Hi! I think it depends. It depends on whether you're a natural who straightens or not. I don't straighten my 4b hair and my edges are as thick as my crown. I also don't wear headbands with teeth that puts stress on my edges (that was a hard lesson learned).
I think genetics also plays a role. I have a friend who's natural and straightens but she inherited her dad's thin hairline. Other than that, her hair is full and beautiful.