From the moment Sir Isaac Newton sat in that orchard and witnessed an apple falling from a tree, we became acquainted with an unyielding law: the law of gravity. What goes up, must come down.
Pretty much everything that flies has a weight limit. This is because of the properties of flight, including parachutes, balance air resistance (drag), lift, and weight. As you may know, objects with a greater mass fall faster than objects with a smaller mass. Until any falling object encounters an amount of air resistance equal to its weight, it will continue to accelerate. An object that weighs more thus experiences a greater force of gravity and will accelerate to higher speeds before reaching terminal velocity. Simply put, the more massive the object, the faster it will fall! Ipso facto, the more massive the object suspended beneath it, the more surface area, drag, and lift the parachute must have to safely bear the load of the weight.
If you’re wondering, why not just create a parachute big enough to carry a 300-pound skydiver and his tandem instructor? (Read more about tandem skydiving here.) Here’s the kicker: the larger the parachute, the more it weighs. In this case, the only potential solution exacerbates the problem. This is why parachutes are only made up to a certain size.