How to stop ads from opening App Store on my device?

I’m watching an ad in a game, and all of a sudden, it opens the appstore. Why is that even allowed? Now it’s the appstore, tomorrow can be my bank app. I mean, apple is all in for privacy and security, how can this even be possible? And more and more ads are doing this. If i wanna download that game/app, i know what to do. I dont need the ad to open an app for me. I have no idea how and why apple allows this.

[Re-Titled by Moderator]

Original Title: why is an ad allowed to open an app