Half a day on the internet..... No, I don't presume much at all, from the sounds of it.
I 'taught' myself dovetailing in 3½ minutes from the internet... But I guarantee you that neither I nor anyone else will be anything like as good at it from those 3½ minutes as the guy in the video who's been doing it for decades.
What you mean is you learned about how it works... but even then, knowing how and having the skill to do it well enough are vastly different. Many things take more practice, skill and experience rather than simple knowledge, and without them in sufficient measures you will **** it up to hell and back.... perhaps even injure yourself in the process. That's just the way 'trade' stuff goes.
And even if it weren't, people are good at different things and some just don't have the head for it... Plenty of über smart folk here at work with degrees, diplomas, doctorates and all manner of fancy engineering qualifications, who can't even keep their shoelaces tied, much less sew up a hole in their shirt... and you can forget ironing said shirt!
Because if a joint bursts while you're out and you come home to a day's worth of flooding, you have them and their insurance to claim off.
Because it's about more than just whacking an olive and compression fitting on a bit of pipe.
Because it means getting down on the dirty floor, behind the kitchen cabinets.
Because they don't want to do it themselves and can afford to pay someone else.
I've known someone drive over 45 miles and pay £20 just to have a trusted mechanic change his windcreen wiper blades. He's not thick or stupid in any way and I even found him a 2-minute video on how to do it. He could have gone down Halfords, bought the blades and fitten them himself in less time that it took to drive over.... It's just not what he wanted.
Your presuming again, not everyone can't take to things that's fair enough but there are a few that have the mindset to be good at a lot of things with a little practice.
I've always been like that quick read of something do it a few times and that's it.
Don't think everyone just watches a short clip and then do a bodge job. I devote hours upon hours of practice and reading up, talking to people in the trades that I do trust, I just like to do things myself.
Some people think changing a plug is a job for the electrician, others think it's easy.