These examples are frequently cited as evidence that the Oxford comma is essential:
What they show is that sometimes, the writing would be clearer with the comma before 'and'. It's true; it would be. But there are also times when it would be better without:
Those at the ceremony were the commodore, the fleet captain, the donor of the cup, Mr. Smith, and Mr. Jones.Here, the sentence could read as if Mr Smith donated the cup, but he is meant to be just another person in the list.
And then there are times when you'd have to be some kind of weirdo to misunderstand the meaning:
Note, of course, that all of these examples are only ambiguous in writing. In speech you have different intonation patterns to tell you what the meaning is.
What this boils down to is people on the internet wanting a rule that they can blindly apply and then criticise those who don't know it. What would be a more sensible strategy would be if people just read their work through and applied punctuation where it helps to make the writing better, and not where it doesn't.
(FWIW, this excerpt from Mental Floss seems to get the balance about right: 'George Ives, the author of a 1921 guide to the usage style of the Atlantic Monthly Press, ... [shows that] making the comma before "and" standard practice is more economical. This way, the reader will know for sure that if it's missing, there's a good reason.')