Well technically one is a new arrival (today) the other two came just after the New Year.
First to arrive were two promos purchased from Board Game Geek (BGG) for the games Alhambra and Tokaido (top half of the photo). I like that BGG gets promos (not all sadly) to sell. Most promos are gained from attending conventions (majority based in the US). So the only chance to get one is either eBay or BGG. BGG tends to be the kinder option of the two selling the promos at a reasonable affordable price.
Promos aren't necessary for a game. There said it before someone else did. So why do I like them? I have a character flaw. Sadly companies exploit people like me. My flaw? I'm a completesionist (is that a real word?) If I like something I have to have all the bits for it, expansions, promos, different covers (if comics), appearances (even if it's a single panel in a comic). So you get the picture. Yeah I'm weird. Besides my flawed character, promos add a little variety or new options to a game. For example the Takaido promo I got adds a new character for players to chose to play with. While the the Alhambra promo adds new tiles (buildings) to purchase.
In the later half of last year Fantasy Flight Games (FFG) announced the Scum and Villainy faction for the X-Wing miniatures game, which is wave 6 iirc. Now the Scum and Villainy version of the Aces packs for the Imperials and Rebels comes with extra cards etc that convert one or two ships to the new faction if you want to use them with the new faction. One of those ships that can be converted will be Slave-1 which I didn't have. Now the ships in X-Wing have print runs, and if you try and get a ship between runs it can cost you a lot more (depending on how desperate you are) than the rrp. Luckily Slave-1 and the Falcon (already got) have just been reprinted and the container ship has hit our shores and the contents distributed to the game stores. Which means these ships can now be bought for a sensible price again. Hence I've bought the Slave-1 while it is available. There will be many like me that will have waited for this reprint, and snapping up the ships at the correct price. Which means they will sell out quickly again and become scarce and expensive once more. It's a vicious circle.