I subscribe to a dedicated Yamaha keyboard message board. It's handy as there's lots of "how to do it" tips as some of the keyboards (like mine) owned by contributors are very sophisticated. (I can only understand half of what's in the instruction book, but I get by). I would imagine most of the contributors, as am I one, will be senior citizens. There's an opportunity to upload individual performances, where people can comment on them. No one ever makes critical remarks. I've often on other message boards criticised the performances of once great artists, when they don't know when to call it a day. Here's a typical example from this board where someone "should never have started." There's no end of them. I'd be embarrassed to post that. But I wouldn't post a criticism on that board. I know I've no voice now, so I wouldn't even try. Like many, my keyboard can be set to swop around registrations with the touch of a button during a performance, no need for "double tracking.". If you want "voices" these keyboards can sing far better than anyone. Here's the same tune with a better chord structure. I've actually tried to copy part of the sax solo on the record by “Boomie” Richman, a veteran of the Dorsey and Goodman bands. This from five years ago. https://app.box.com/s/ih0cr8bdmatn5vyofm7tj108t5kqfzqe
I can't speak for anyone else. No, I did not listen to either one you posted. But a guess would be that they have a dream to be someone, to be a real musician. I am a self taught pianist and organist. I play for my church. I am not Mozart, Beethoven or any other great musician. I would not even dream of posting a recording of my playing on you tube or other website. But some like my playing. I recently bought a used violin that needs new strings, new bow strings, and a bridge. When I get some, I will try lessons on you tube. I have always wanted to learn piano, organ, and violin since I was a little kid. I don't know if I can learn violin or not, but I hope to try soon. My sister taught herself violin (and piano and organ) before she died. Have you ever had a dream that consumes you? Maybe that is why they post.
You can tell from their voices, that they are likely to be over forty or older. With any instrument, including voice, the two most important tasks (in my opinion) are to stay in tune and be able to hold long tones. Few amateurs can do this. Here's another well made video, (well what's wrong in adding a couple of extra bars?) but I'd be embarrassed.But maybe I'm too critical?