How are WW1 or WW2 era bombs still regularly found in gardens and houses around UK and Europe?

Question

The day after or week after these were dropped 60-100 years ago, did people not think, there’s a bomb over there we should make it safe.

Edit: I singled out the UK because they discovered a bomb from World War Two today in Plymouth. I know the UK is still in Europe.

In: Other

Answer 1

Were i live in nothern germany, you are not even allowed to magnet fish, because we don’t know how many unexposed bombs are still in the seas.

There were such massive amount of bombs dropped that nobody was able to keep track of all the unexploded stuff, if they even knew it was there. Rebuilding from rubble and covering up ruins was done without checking at some point.