Lame excuses

Yo~ Why humans keep giving excuses when they had done something wrong? Why can't they just admit their fault? What are they afraid of? Because of their fame? or what? I don't understand. Saying 'sorry' is it really that hard. I wonder.... My housemate is one of the type. His sink was broken. So, of course, he need to pay for it coz he is bind to the contract. But, he is giving such a lame, unreasonable and ridiculous excuses, saying DEPRECIATION!! Ya, some things depreciate. But, it's a ceramic sink. I don't even see my house sink broken unless it is knock by something which is hard or heavy. So, what kind of excuses is his? Unacceptable. Really feel like giving him a slap. Feel annoyed by it.