Ramps make it easier to get to high places. You have to travel a longer distance, but it's much easier to travel on a slant than to go straight up. Think about loading something really heavy into the back of a truck. You could lift it straight up, but that's hard. Instead, walking it up a ramp would be much easier, even if you have to go a little farther.
Science and skateboards? Here's a short clip from a longer video about simple machines. This one just focuses on ramps, or inclined planes.