...a dagger deals 1d4 damage, and these types of players rarely extend the logic to say "I stabbed that 13th level fighter with a knife, why isn't he dead?".

This is a common and basic misunderstanding of how HPs are/were intended to represent the combat stamina of a creature.

Originally, they were a design compromise by Gygax & Arneson to measure the combat stamina of a creature within a fight, borrowing heavily from their joint background in tabletop miniatures wargaming. Not only do HPs measure a creatures ability to take physical punishment (wounds) but also their ability to keep moving/dodging/weaving/parrying/mental will/morale fortitude (combat stamina - ability to stay in a fight). Thus, it is a conglomeration of homogeneous fighting concepts represented by a single number.

HP is a single number which unfortunately does not take into account the slow degrading of a creatures combat stamina over time - a creature can fight at 100% optimal fighting ability from 100 HPs to 1 HP before becoming suddenly combat ineffective (dead? unconscious? exhausted?). I hope this explanation helps better understand that HPs in D&D are not just "the sum of all wounds".

...a dagger deals 1d4 damage, and these types of players rarely extend the logic to say "I stabbed that 13th level fighter with a knife, why isn't he dead?".

This is a common and basic misunderstanding of how HPs are/were intended to represent the combat stamina of a creature.

Originally, they were a design compromise¹ in Gygax & Arneson's "three little brown books" to measure the combat stamina of a creature within a fight, borrowing heavily from their joint background in tabletop miniatures wargaming. Not only do HPs measure a creatures ability to take physical punishment (wounds) but also their ability to keep moving/dodging/weaving/parrying/mental will/morale fortitude (combat stamina - ability to stay in a fight). Thus, it is a conglomeration of homogeneous fighting concepts represented by a single number. This conglomeration was explained in some detail in the AD&D 1e DMG by Gary Gygax (also found in this asnwer at RPGSE).

HP is a single number which unfortunately does not take into account the slow degrading of a creatures combat stamina over time - a creature can fight at 100% optimal fighting ability from 100 HPs to 1 HP before becoming suddenly combat ineffective (dead? unconscious? exhausted?). I hope this explanation helps better understand that HPs in D&D are not just "the sum of all wounds".

¹ A pre D&D citation of the early stage of HP in Blackmoor

...a dagger deals 1d4 damage, and these types of players rarely extend the logic to say "I stabbed that 13th level fighter with a knife, why isn't he dead?".

This is a common and basic misunderstanding of how HPs are/were intended to represent the combat stamina of a creature.

Originally, they were a design compromise by Gygax & Arneson to measure the combat stamina of a creature within a fight. Borrowing heavily from their join background in tabletop miniatures wargaming. Not only do HPs measure a creatures ability to take physical punishment (wounds) but also their ability to keep moving/dodging/weaving/parrying/mental will/morale fortitude (combat stamina - ability to stay in a fight). Thus, it is a conglomeration of homogeneous fighting concepts represented by a single number.

A single number which unfortunately does not take into account the slow degrading of a creatures combat stamina over time - a creature can fight at 100% optimal fighting ability from 100 HPs to 1 HP before becoming suddenly combat ineffective (dead? unconscious? exhausted?). I hope this explanation helps better understand that HPs in D&D are not just "the sum of all wounds".

...a dagger deals 1d4 damage, and these types of players rarely extend the logic to say "I stabbed that 13th level fighter with a knife, why isn't he dead?".

This is a common and basic misunderstanding of how HPs are/were intended to represent the combat stamina of a creature.

Originally, they were a design compromise by Gygax & Arneson to measure the combat stamina of a creature within a fight, borrowing heavily from their joint background in tabletop miniatures wargaming. Not only do HPs measure a creatures ability to take physical punishment (wounds) but also their ability to keep moving/dodging/weaving/parrying/mental will/morale fortitude (combat stamina - ability to stay in a fight). Thus, it is a conglomeration of homogeneous fighting concepts represented by a single number.

HP is a single number which unfortunately does not take into account the slow degrading of a creatures combat stamina over time - a creature can fight at 100% optimal fighting ability from 100 HPs to 1 HP before becoming suddenly combat ineffective (dead? unconscious? exhausted?). I hope this explanation helps better understand that HPs in D&D are not just "the sum of all wounds".