ADHD people are not addicted to media and video games, but rather media and video games work in a way that gives immediate responses which ADHD people need to stay motivated and focused.
ADHD brains are wired for immediate responses. Because ADHD brains have executive function problems often resulting in time blindness and an inability to accurately foresee consequences, ADHD people often have motivation problems. Immediate results and feedback are necessary to motivate ADHD brains. That's what media and video games give: they give immediate feedback to ADHD people's under stimulated brains.
Why can a young child with ADHD pay attention to a video game for hours but can't focus on his math worksheet? That is because when he finishes a video game level or race, there is fanfare and a prize. It feeds his need for an immediate, positive response. If he finishes his math worksheet nothing happens. You can help your child focus on his school work by offering rewards for each problem solved like a sticker or a "That's great!" for every finished part or problem. What works varies by child, but positive reinforcement can go a long way both in motivating the child and helping with their self-confidence.
Additionally, ADHD people have a superpower called hyperfocus which allows ADHD brains to pay extra special attention for an extra-long time to things that the like and things that work well for their brains. ADHD people often don't even realize that we are hyperfocusing. It can be very frustrating and upsetting when our hyperfocus gets broken because we finally found something that is working for our brains! Some ADHD people have actually reported feeling physical pain when their hyperfocus is broken. That is how strong this hyperfocus superpower is! It is no wonder that, with all of these variables, ADHD people's attraction to media and video games is often misunderstood as addiction.