I don't know what kind of emphasis you've seen, but being able to look at a public example of code a person has written is IMO the single biggest risk reducer available to a company hiring developers (well, other than actually having worked directly with the person before, which is an order of magnitude or two less common) because it gives me a picture of performance on real world software. Hiring is substantially about risk reduction because there's a huge amount of stuff you don't know about how the candidate will do. It would be foolish for companies to not take advantage of this potential source of signal. If it's not available, then I would proceed with my normal assessment process. Lack of public code isn't going to disqualify a candidate, but it does help to increase my confidence.