By Byungwook Kim SEOUL (Reuters) – South Korea was the first country to launch a fifth-generation mobile network in 2019, heralding a warp-speed technological transformation to self-driving cars and smart cities. Three years on, the giddy promises are unfulfilled. Some 45% of the country’s people are now on 5G, one of the highest rates globally, after some $20 billion in spending on network upgrades that have boosted connection speeds five-fold. But telecommunications companies have not been willing to invest in the fancier technology that would ramp speeds by 20 times over 4G technology. That…