Is Paypal free?
yes it's free to have an account not only that you can actually use that account to make transactions unlike with bitcoin where if you want to make transactions it cost something. why do you think people use paypal on ebay?
Is using a bank account free?
yes there's lots of free checking accounts from different banks.
With such argument, i would point out it's free to download Bitcoin wallet software. And PayPal usually charge tx fee.
Comparing blockchains to Google and Facebook is like comparing apples to bananas. Does Google and Facebook provide financial services?
Does Google and Facebook have their own currencies.
facebook tried to get its own cryptocurrency and if they had done it it probably would have outstripped bitcoin in popularity. how many users does facebook have? how many does bitcoin have? case proven.
Most people who use Facebook only use it for communication purpose though. So IMO comparing total Facebook and Bitcoin user isn't good comparison. For example, how many Facebook user ever use Facebook Marketplace (where actual money transfer usually happen outside Facebook system)?