I don't think that this is true. The number of unique BTC addresses currently is about 500k, so I'd say that not more than ~100-150k people are actually using Bitcoin.
alot of people have funds in third parties like exchanges which hold hundreds of thousands of peoples funds in only a couple addresses.(cold wallet reserves)
EG just a couple addresses can represent million users funds combined.
oh and by the way there are 250,000 MERCHANTS. before you even start counting users.
Maybe you're right, but the number of the BTC daily transactions never exceeded 300k. I am sure that millions of people know about Bitcoin, but I'm not sure if millions are using it.