Because 99% of the time, the simplest solution is the best one, and the simplest solution never involves blockchain in any capacity. In this case, the simplest solution involves money. Currency exists for a reason, whether you like it or not.
Also, for real-world use, not being able to alter information in the system is a bug, not a feature, because it prevents the correction of mistakes. And there will always be mistakes, because humans.
Heh. Life is once again attempting to imitate xkcd.