before Pesach your house is entirely cleaned, EVEN ONE CRUMB of Chametz is not allowed.
In most respects people feel this way like in the case of the one shmutz in the Library of Seforim.
But it seems in this one issue people are willing to look away , put their heads in the sand , make up excuses and do anything except find that one crumb before Pesach.
That is what I dont understand, I dont think the house is full of Chametz, It was cleaned. But that crumb is still there and you are required to search for it COMPLETELY