At my casino the rules are:
- If you reach showdown in a cash game, the last aggressor shows first. They have the option of either showing or mucking. The other player is not required to show their cards to win the pot.
- In a tournament, all players must show their cards in an all-in situation, but this is not the rule for cash games.
- There is a "show one show all" rule whereby if you show your cards to one player, then you must flip them over for everyone to see.
The last two are pretty standard, but the first one has something that's not the norm: usually you HAVE to show your cards to claim any part of the pot, even if your opponent has mucked and you're the only one left, for game security / anti-collusion reasons.
Incidentally, are you from Melbourne Australia? If so that'd mean you're talking about Crown right?
Technically the last aggressor doesn't have the option of mucking there: the poker room rules state clearly that "the player being called will then expose his/her cards" (12.5.4,
https://www.crownmelbourne.com.au/g...wn-Melbourne-Casino-Poker-Rules-V13.pdf.aspx). There's no "unless they want to muck" option, it's just stated that they
will expose their cards. It then says that the other player(s) will show their cards if they're holding something of equal or higher value.
Now I know from experience playing there this isn't always what happens: quite often you'll get to the end of the hand and the players will just stare at each other in that "you show - no you show" way, sometimes they'll be even more obtuse and say something like "I've got a pair - so do I how big is yours" and generally waste a bunch of time until the dealer insists that somebody turns over.