We already do follow UTC where it matters - global systems, operations, etc.

What problem are we even trying to solve? People want noon and midnight to make sense, and every region has customs around what time offices are open and when events happen, etc. Nobody cares what time it is in London - nor wants to overlay London's time onto their own thousands of miles away.

For any application where someone else's time zone is important (setting up a work meeting across multiple continents), the software already shows you everybody's time zones and working hours.