K.R.
have you tried the other kinds of cups RECENTLY? My daughter used to use the soft silicone ones too, but I later tried the hard plastic top Gerber cups and they are awesome for not leaking! You can try the straw type too.
Personally, I let my daughters have their sippys in the living room when their playing after breakfast or dinner, but that was never the case with the silicone ones b/c like you experienced, they leak a lot (esp. since my daughter broke it sticking her finger in the hole too! haha!). There is nothing wrong with a rule that cups stay at the table.