Scihub is not exactly mainstream so nobody should expect that "laymen" would be downloading science papers. It grew out of need. I think the usage statistics have more to do with how early in time a country's scientists learned and spread the word about it.
That's interesting that you say it's not mainstream. Most of the people I know currently studying for a Masters or PhD have told me it's what they plan on using once they no-longer have access to the University publication systems after they graduate.
Most people currently studying for a Masters or PhD aren't "laymen".