Why Are Certain Coins Called “Junk Silver”?

By GovMint :

In numismatics, the term "junk silver" describes coins in extremely poor or heavily worn condition, to the extent that their numismatic value is minimal. While they may be in rough condition, such coins are still prized for their intrinsic precious metal content. Typically, junk silver coins are sought after by stackers and precious metal enthusiasts primarily for the silver or other metals they contain rather than their collectible or aesthetic appeal.

Sources Used:

https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications 

https://www.coinflation.com/coins/1909-1982-Lincoln-Cent-Penny-Value.html