Most significant thing about El Salvador making BTC legal tender

Making BTC a legal tender means that in theory, BTC will never have to be converted into another currency, that is, they will never have to be sold. Over time, many thousands of BTC may be circulating in the country without ever being put on an exchange.

When the vet hospital being built with profits was mentioned, someone said, no, they should just hold. But it may be possible that they intend to pay the builders, etc. in BTC in which case the coins never need to be sold. If other countries, say Argentina, produce medicines that vets use, then BTC can perhaps be used to pay for those and again, no need to liquidate.

This sort of thing has never happened on a large scale. The economy of El Salvador is not huge, but it could tie up a lot of BTC and as more countries are added who use BTC as a legal tender, I think you get the picture.

EDIT: One important idea that just occurred to me is that the more goods and services available with BTC, the more that will become available; the effect snowballs. If you buy from a company that has to buy what it needs with fiat, then it is more likely it will sell the BTC it receives from you. But if the company finds that even one of its suppliers accepts BTC, then it will retain (perhaps) some portion at least of the BTC it receives to pay for that material, etc.

It is obvious, I think, that this effect spreads rapidly as a greater variety of companies accept BTC.