Nylon, chemically a polyamide, brings a combination of toughness, puncture resistance, and abrasion resistance that polyethylene and polypropylene cannot match at comparable gauge. That strength is why nylon shows up disproportionately often in packaging for bone-in meat, sharp-edged products, and vacuum-sealed applications where the film has to survive direct contact with hard or irregular surfaces under pressure.
Nylon also offers a useful, moderate oxygen barrier on its own, better than polyethylene but well short of EVOH, which makes it a reasonable middle option for products needing some barrier improvement without the full cost and complexity of an EVOH structure. It has poor heat-seal characteristics by itself, similar to BOPP, and is generally coextruded or laminated with a polyethylene sealant layer. Nylon is also notably moisture-sensitive in terms of its mechanical and barrier properties, absorbing ambient moisture that can change its flexibility and gas barrier performance over time.