You can’t make sales people responsible for the entire company, that’s CEO- and board-level responsibility.
If you don’t give sales bonus for clients that later canceled due to engineering or tech support fuck up, do you expect regular sales people also to do engineering and tech support management in your company?
It is only a counterpoint if you claim that this compensation scheme works well. If you don't think it makes sense, then it actually proves my point that bonuses should only involve things that directly depend on employee's own performance.
If you don’t give sales bonus for clients that later canceled due to engineering or tech support fuck up, do you expect regular sales people also to do engineering and tech support management in your company?