I 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.