I can’t see how attaching them wouldn’t increase the rates at which they’re recycled.
You can believe this was never a problem perhaps, but then you’ve got to wonder why the change was made—no one is gonna profit from the design of bottle caps changing, so what’s the motive for the change if it’s not a problem? Contrary to the somewhat common belief, politicians tend to try and not waste time on useless legislation.
A refund system costs money, this change basically doesn’t.