I've never understood stacking. I guess you could say I've always been over it! Like others have said, I think it takes away from the individual pieces and cheapens the overall look.
I love jewellery and wear some daily but I do often find it annoying to wear even one of each type, so to have multiple stacked would kill me. Could never do it for rings as I can barely handle wearing one ring due to very sensitive fingers. With bracelets I much prefer to wear one overall or one on each wrist - something dainty so it doesn't irritate me while I'm typing at work. The tiffany bead bracelet is perfect for that. Anything more and I can't stand it. I will only wear 2 on one wrist when I'm combining this delicate chain bracelet with a bangle that's just a bit too big and needs something else to stop it. As for necklaces I think one is definitely enough and I'm surprised everyone doesn't get their stacks tangled! My sister tried to wear 2 necklaces for the first time and they ended up tangled and then when she tried to untangle them one of them broke! It's also a worry to have two pieces rubbing against each other and creating scratches. So overall, I am very against stacking.
But to each their own. Yes, I'm sure it makes jewellers happy to see there is a stacking trend