[Nyororin]

I think it`s because it is a firmly followed rule. You never, ever enter someone`s house with shoes on - no matter what the reason is. You will even hear stories of catching burglars because they took their shoes off at the door...
There is a specific dedicated area inside the door solely for this purpose.

For a while in my house in the US, we took our shoes off when coming in (mainly to avoid getting the carpet too dirty) - but it wasn`t an absolute rule. Friends who never took their shoes off, well, never took their shoes off. Someone coming to do work in the house would wipe their feet on the door mat, but not take their shoes off.

I don`t know how it is in Canada, but is it a 100% rule that no one EVER keeps their shoes on for any reason?