I used to have a very fruitful open source life. I have a personal website, a blog, etc. Some of my libraries are useful and reasonably known on my niche.
Then I had a child. Everything changed after that. I suddenly don't have time or energy to devote to open source any more.
I am the same person as before, but if you looked at my online activity before and after, it's like two different people. If you "give points" to the person who had a lot of personal free time in the past, you'll be missing the one who doesn't know (but is just as capable, he just has other things to do, or less free time).
With students it's the same deal. If you give points to the ones with a very strong online presence you are prioritizing the ones which have the luxury of free time to invest. You will miss on the ones who, say, are taking care of an elderly person, or have to work in the cafeteria every day after class in order to make ends meet.