CPP is a pension plan. OAS is not.  As CPP is a fully funded pension plan, not a tax funded welfare payment.  

There should be some form of survivor benefit. Most pension plans allow for 50% (or thereabouts) survivor benefit, with no cap if "you already have a retirement income". The problem appears to be that the maximum payable is set at the same level as that for one person.  Raise the cap to allow for two income families to benefit from 40 years of contributions.