If you're in Canada, you are not expected to attend the interview, and the visa officer won't hold it against you if you're not there.
In my case, I was visiting my husband when he was called for an interview, so I went with him to the embassy. I had to wait outside, but after about two hours, the visa officer called me in and interviewed me too (my husband had to wait outside.) His application was rejected because the visa officer didn't believe it was a genuine relationship. My lawyer told me it would probably have been better if I had stayed at the hotel - she said it is highly unlikely they would have called me, and if they only interview one spouse, there is no chance of contradictions.
