In a perfect world, Bitcoin availability is 21,000,000 --- but this isn't a perfect world and a lot of wallets are lost due to a multitude of factors, such as:
1. lost or destroyed storage (harddrive, usb stick,etc)
2. lost or destroyed keys
3. the owner died (this has increased since COVID)
Of course there are other avenues for permanently lost Bitcoins, but these are the first that came to mind. This illustrates that there will actually be an unknown amount of Bitcoin that is just gone forever, so the 21,000,000 figure is actually lower in our imperfect world.
This chart shows the amount of Bitcoin available on exchanges for sale. You can see how the supply on exchanges has been dwindling and the general behaviour pattern is (as illustrated by the data) that the price of Bitcoin will go UP as the supply on exchanges goes DOWN.
The current amount of Bitcoin available for sale on exchanges is sitting around ~2.1 million (look at the chart), this is only 10% of the 21,000,000 and we already discussed how there wont be 21,000,000 Bitcoin available due to real life situations.
To put this in simple terms, the smoothbrain shills and the nocoiners are big mad because of this and will say anything they can to dissuade you from learning about Bitcoin and getting Bitcoin because they don't want you to have any future in financial freedom. They are greedy and late to the party...they are 'that guy' just being an awkward ass in an otherwise great occasion.