kds ji
This is a good question, and I have myself wondered. There seems to be more than one reason. Both cultural.
Think about the responsibilities of Sikh woman at every level of society in almost any country, except those who are highly educated and who do not have careers of some kind because they do not have to work. The time and energy for forum participation is not there for most. Particularly after they go onto school or marry and start families or both. All of the Sikh women that I know personally are up at the crack of dawn, taking care of family and are then off to their jobs -- most of which are professional in nature so they take work home with them. Then back at home they have more family issues (supervising homework, cooking, planning the next day). On weekends - shopping, participating in Gurdwara activities. They never never never rest. Until they are older.
The older women probably do have more time, but they are also products of cultural expectations that women should slip in and out of situations silently like shadows. This is not about Sikhism but about culture.
Anyway, the next time I see a Sikh woman shepherding a bunch of kids into an SUV and driving off anywhere on a Saturday morning I will remember that she was cleaning up after breakfast, tying hair and padkas, keeping everyone on task, and the Internet was the last thing on her mind.
After the bull who holds up the world, there are Sikh women holding up everything else.