alt Hacker NewsI assume it is a relevant enough concept to flying an aircraft (which also happens to be the context of TFA) that you learn about it while flying.
I guess another thing worth noting is that "glide ratio" isn't the same as "gliding" in the "flying a glider" context.
The space shuttle is probably the most famous glider, and was described as "a flying brick" and getting it to the ground at the right spot was very much a matter of glide ratio. Worth noting the space shuttle's speeds started off as hypersonic.
By comparison, a typical glider's built to be able to take advantage of air currents to regain altitude, and I'm not sure how weight affects that.
Weight affects speed with minimum sink. That affects the diameter of the circle you fly. Since thermals have more lift towards the center (assuming perfectly circular thermals), you are not able to circle in the strongest lift. So you climb more slowly.
You can glide faster with the same L/D, so that might be worth it if you try to optimize for speed.