True. We don't ask for GitHub links because they are pointless from a screening perspective. I'm happy to talk about them during an interview, but if I see a github link in a CV, there's little chance I will visit it. (Source: I'm a hiring manager at a tech company, have been in a similar position at previous jobs for several years).
The fact is, as a hiring manager, I would have no time at all to do anything if I start looking at all my candidates' github links. I would be more than happy to look at a portfolio showing products built by them, if they look interesting, I can ask technical details during the interview.