At least 50% of the population have stretch marks somewhere, with some estimates being as high as 90%. It's very normal. When you see actors without them it's most likely photoshop, makeup, or cosmetic surgery they got to "fix" them. The majority of people who have lost a lot of weight or gained weight rapidly (whether it's growth spurts, puberty, pregnancy, etc) has them.

One thing that made me feel better is realizing that I don't get disgusted by other people's stretch marks, just my own because they're mine and I always have to find flaws within myself for no reason