Why can't ED instances have persistence?

I am generally curious about this. If an instance is created when a player drops to 'normal space' and something is left behind when they leave - such as a canister - why can't that instance be persistent for other players that come into the same system?

All it would take would be to store the instance location in the current system, and the contents and location of contents in the instance. Then anyone who drops into that instance can see what's there and makes it 'live' for current players.

It seems like this type of persistence is doable, and would provide a huge amount of variety to the game.

Player created instances can decay over time, but it would be more like playing on a large 'minecraft' server, where you can see some trails left by other players.