I really wish we had a culture of portfolios like other professions do. Of course, it's hard to do this because of the nature of our work; the code we create every day is not only company property that is generally kept secret, but is very hard to judge the quality of by means of a quick review with no sense of context. Furthermore, if you choose to merely judge the products the person has coded, assuming they've coded the lion's share of it, it's hard to tell what is going on behind the scenes and any judgment would be based on hypotheses, which would generate tons of false positives and negatives.

Still, something like portfolios are a very practical way of evaluating candidates because you're looking at real, concrete things the person has actually created. A modern coder interview is more like kicking the tires on a used car and then immediately deciding if you want to buy it or not.