By the globe stats, there is a 90% of ignorance rate of candidates' replies. The reason is the template emailing which is snowing them under hundreds of emails weekly. It happens because recruiters have a lack of information about candidates. Mostly, tech guys haunt GitHub, there are their skills, interests and repositories, so it is relevant to analyze this information to know whether you need to contact the candidates.
This
article will be handy to see that.