I've been diagnosed with it and find medication incredibly helpful but must confess to some ongoing scepticism.
The diagnostic process isn't just about identifying traits; it is about identifying whether those traits have had a significant lifelong impact on your ability to function in different aspects of your life.
The trouble is that what counts as 'functioning' is incredibly subjective. I also think that the way the job market is structured, increasing living costs, changing expectations of parenthood and the pressure to appear perfect social media have all played a role in creating a really demanding and narrow definition of 'functioning' that a lot of people are going to struggle to meet, leaving them to feel like failures a lot of the time and to naturally question whether there is something wrong with them.
Any human trait, including the clusters of traits we now think of as types of neurodivergence, is going to be distributed unevenly across the population. Whether those traits get labelled as a problem or not partly depends on how severe they are and partly depends on the environment a person is operating in: what is expected of them by others and what they expect of themselves.
I have always struggled with what others seem to see as the basics of life: personal care like regular washing and tooth-brushing (let alone sorting hair and makeup); basic conformity to essential aspects of school and work (being on time, meeting deadlines, following procedures); maintaining a half decent living space; managing money; remembering to eat any meals (let alone to cook and to have 5 fruit and veg a day). I've always been good at some stuff like processing lots of written information quickly and writing long reports, and solving certain types of problem when adrenaline is flowing, and that has helped me to keep my head above water to some extent. But now I have a stressful job and a marriage to nurture and an unwell relative to care for and a wonderful child who I want to raise well, and so what counted as 'just about functioning well enough' for me 15 years ago when I had few life responsibilities doesn't count as 'well enough' for me now. If I were to put pressure on myself to have a picture perfect home at all times, to excel in my job without making a single mistake, or to live up to my own ideas about a perfect mum and perfect wife, I would feel even more like being at the bottom of a huge dark hole of failure.
I don't think it's any wonder that life transitions like motherhood or caring responsibilities or more seniority at work make a lot of people question whether they might have ADHD because objectively the demands have increased.
I also think that ADHD offers a compassionate way for a person to view themselves as opposed to the brutal alternatives of seeing yourself as lazy, inadequate, incompetent and generally a bit shit. It's no wonder people would prefer the ADHD option.
I'm not saying ADHD isn't real - just that social context matters. And I reckon that most people would be more productive on stimulants!
And to address your actual question (sorry for the tangent!), I know almost no one who thinks they have ADHD out of a wide circle of colleagues and friends and acquaintances, which isn't in any way scientific but just provides a counter-narrative to the idea that this is somehow taken up everywhere.