asking people to store something for a very long time is very hard. Take the nuclear waste from the US atom bomb tests in the pacific. They capped the thing w/ tons of concrete but sea level rise and cracks are making it inevitable its going to cause a mess. And thats literally less than a century ago. The half life of these things is tens of thousands of years.

I think you underestimate how 'temporary' many seemingly strong structures are and how high the temptations to cut costs are. Its very easy to be like "welll...this'll probably hold. I'm sure of it."