It's amusing how quickly we start taking things for granted. Right now SpaceX is the only company that recovers their orbital class booster. And that didn't ha

It's amusing how quickly we start taking things for granted. Right now SpaceX is the only company that recovers their orbital class booster. And that didn't happen until 2016! Prior to that, everyone dismissed landing rockets as impossible. Given the lack of competition for launch vehicles + the fat defense contracts being awarded, there wasn't much incentive for the incumbents to even try to bring the cost down. Designing a rocket that can land and be reflow is a multiyear process. As other comments have said, more design changes would been needed to F9 to make it more reusable, those changes have tradeoffs. Instead, SpaceX chose to invest in a new design and more capable vehicle. Other launch providers like RocketLab and Blue Origin are pursuing reusable vehicles. "Why has no one done it?" give it time... it will happen sooner than we probably expect.