Complex sentence: Plastic casks are increasing in popularity because they are cheaper to buy and lighter to carry, though they don't last as long, they are also less likely to be stolen as they have no melt-down value.
Split into simpler sentences: Plastic casks are increasing in popularity because they are cheaper to buy and lighter to carry. Though they don't last as long, they are also less likely to be stolen as they have no melt-down value.