Hi Ersta and thanks for raising these questions. In answer to your points....
First, thanks all for your effords to reply to my post. I disagree with the rule because not showing your cards is part of the game too.
This is very true. But in the case where on the river you bet and I call your bet I'm doing so with the understanding that at the very least I will be able to see your cards
since I called you.. Hence the phrase / idioma / or saying "I paid to see that hand". But it's not that I literally elected to "pay" to see the hand, I just called the bettor on the river and I have an inalienable right to see the hand if I so request.
About folding the winning hand.....I also believe that mistakes caused by stupidity, ignorance or mere inattention are part of the game, so folding a winning hand is the player's own responsibility.
Absolutely it is, that's why the TDA membership never adopted either "winning hand must always be shown" or "all cards must always be shown". The only exception recognized being the case where there is aggressive action on the river... callers of that last aggressor have a right to see his hand on request because they paid (called) the bet amount.
But when I read rule 17b (and maybe it is because my lack of understanding the English language, I am Dutch) I read that the reason the better/raiser has to show, is because the other player "paid to see".
Again, this is a "saying", the reality is "the other player called the aggressor's bet". We just shorten that up with the saying "I paid to see that hand".
This rule was actually adopted at the 2013 TDA Summit but was only formally written into the rules in 2015 after some other related language was cleared up. Perhaps someone can find the footage from the 2013 Summit videos on this topic, it's very interesting discussion.
Thanks again for your post!