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

How would you know there is a bomb over there? There have been fired billions (with a b! Not an exaggeration!) bombs of which around a fifth didn’t explode. So we are still talking about hundred of millions of shells and bombs not exploded. How do you imagine tracking any of those? I think you are underestimating the amount of bombs and shells fired in both world wars by a few orders of magnitude