It is not a meme, is how accounting works, is how governments tax. If you look at your own example, some people though that they had made a lot of profit with Enron, if they did not sold the shares then they only got losses.
Because the you only win or lose money when you sell your shares (not counting dividends if any).
UK law: "You’ll need to work out your gain to find out whether you need to pay Capital Gains Tax.
Your gain is usually the difference between what you paid for your shares and what you sold them for." - https://www.gov.uk/tax-sell-shares/work-out-your-gain
Until you sell there is NO gains as price varies in function of time. And it can go up or down.
The other claims are more complicated. It's difficult to discuss them if common accounting knowledge is not understood.
