More often than not (that's the impression I got anyway), the applicant attends the interview without the sponsor. Usually for practical reasons - the sponsor is far away and it would cost too much. So if you didn't go with your wife, I'm sure it wouldn't be an issue, especially if it's because you are in Canada. As a PR, you should maintain residence in Canada to sponsor someone.
Sponsors who do come with the applicant are more often than not ignored though. Even if you go with her, you will not be allowed to attend the interview - you will be left outside the room where the interview will take place. And you probably will not get to answer any questions yourself.
If there is doubt about whether or not the relationship is genuine, the doubt is usually on the applicant, not the sponsor so it's the applicant that has to defend themselves. While you showing up might confirm to the IO that you are committed to this relationship, it's likely that the doubt was never on that.
I think the biggest benefit of you going would be the emotional support for your wife. The interview is a very stressful experience, no matter the circumstances and can help to have someone there to lend their shoulder. So if you can without much difficulty, I would go with her.
On the other hand, if I had to attend an interview, I wouldn't expect my husband to come - I would rather the $1000+ that he would have to spend to get there was spent more efficiently.
If you don't go though, be sure to be available by the phone during the interview. Not sure about your wife's visa office, but some others have called the sponsor by phone during the interview to answer some questions and it's better to be available than not. Your wife can tell them you wanted to come but could not, but you are available to talk to if needed.
