Prevention of varicose veins

It's not very severe, but the blood vessels are protruding and visible, which is very bothersome to the eyes.

On top of that, the stretch marks on my thighs are so severe that I can't even wear shorts. Once they appear, is there no way to fix them except surgery?

Is there a way to prevent it from getting worse?

I don't have a job that involves walking a lot, nor do I strain my legs excessively, so I don't understand why it's like this.

Please let me know if anyone knows any prevention methods.