Why are stretch marks seen as a flaw?

CubsterShura
Why are stretch marks seen as a flaw?
I have stretch marks on parts of my body and they are mainly from two life events: 1) When I hit puberty and my body started growing and 2) When I started doing martial arts class and lifting weights, they added stretch marks on my legs. A lot of men also have stretch marks from gaining muscles in their upper body.

Another common reason why many women have stretch marks is because of pregnancy. Which, again, is not a bad thing at all. In fact all these reasons are... Great! They are all amazing things!

The only 'bad' reason for stretch marks is excessive/rapid weight gain/loss, or frequently fluctuating weight.

So then why are stretch marks seen as a bad thing that needs to be reduced, or hidden?
Why are stretch marks seen as a flaw?
75 Opinion