What is keeping us from anchoring a cable to Earth’s surface and tethering a platform in space?
The main reason we haven't done it yet is that there's no practical way to do it. You'd need an incredibly strong cable to withstand the force of gravity, and you'd have to deploy it from a very distant location - probably somewhere in orbit. And then you'd have to install a platform at the other end to hold your payload. That's just not feasible today.