Neuroscience answer: Dopamine is responsible for (among other things) motivation and the feeling of reward when you do something. People with ADHD have chronically low dopamine levels because they have more dopamine transporters than most people do in their brains, so their brains burn through it quickly.

In practice, people who are unmedicated tend to do whatever they can to try and get a little more dopamine to get them through the day. It’s why smoking, risk taking, illicit drug use, gambling addiction, etc are also correlated with ADHD: all those things give you a dopamine boost.

So when someone is sitting there scrolling through memes on the phone, they’re hunting for the dopamine. The dopamine is almost never at The Task. It’s incredibly frustrating to understand all that and still not really be able to do anything about it until it escalates into an emergency, at which point you don’t really need dopamine to deal with it anymore, now that you have adrenaline. But that’s obviously an unsustainable way to do things on a regular basis.