It is the family pathway which is available only to very small communities whose (mostly) brothers immigrated to the US in the 80-90s. That's because afaik, it

It is the family pathway which is available only to very small communities whose (mostly) brothers immigrated to the US in the 80-90s. That's because afaik, it also has a 20-ish year waiting. So the convenience store owners are very likely to be folks from this group that are getting green cards for applications they put in when they used to young. There is a reason they all seem to be old men. Most young Indians at these stores are part-time workers on visa studying at universities nearby. For the last couple of decades, a US university degree -> STEM job is the only way known legal way for an Indian to come to US on their own merit. I specify STEM, because none of the other professions get the STEM-OPT (3 tries at the low-probability h1b lottery vs 1 try for normal students), so most US employers blanket reject candidates in non-STEM professions.