I think there are all those factors.
To start, the sign up process is slow since it is still manual.
Secondly, I think people resist change. I have told a number of people about it who were like "eh, looks interesting". People either do not care or do not want to change.
Then there is the it is a scam crowd.
And yes there is a lack of recognition and people simply do not know about it.
As for the number, yes it is ridiculous to think how high this can go. We are on one of the best blockchains out there, handling upto 2M transactions without even breathing hard. There is an active community that is actually creating stuff that results in transactions. And we have many developments in the works which will only add to this entire ecosystem.
I predict we will be blown away in 24 months with what this place turns into. There will be so much on this blockchain it will make our heads spin.