The RPG tradition that has probably puzzled me the most is that physical prowess is nearly always divided between two character attributes. One is invariably called Strength and usually determines melee damage and carry capacity. The other goes by names like Constitution, Vitality, or Endurance and determines things like hit points and damage resistance. It has been so ever since the first D&D rules.
It’s so strange because it makes so absolutely no sense yet is so persistent. Not counting JRPGs (where the player usually cannot alter attributes directly), the only RPG I ever played that did not have these dual attributes was the browser game Dragon Court, which has only three attributes: Guts, Wits, and Charm. Even Diablo, with its vehemently simplified mechanics, drags along a useless Vitality.
It makes absolutely no sense. It does not increase the plausibility of game mechanics, for in man and beast, the ability to deal and to take blows is usually closely connected. It does not enhance gameplay, for where a glass cannon or a purely defensive character is desired, other game mechanics can deliver this far better. In Fallout it was especially counter-productive: Even a stat combining the functions of Strength and Vitality would have been, given the game mechanics, less important than Intelligence or Agility, as it was, the imbalance was even greater.
There are other examples of attribute splitting, but they are less persistent and make more sense. That Wasteland had Agility and Dexterity as separate stats is absolutely unique. I guess Ken St Andre felt that a post-apocalyptic game with no magic needed at least separate attributes governing melee and ranged combat.
More common is the split into intelligence and wisdom for magic, another D&D heritage. It was originally probably introduced to give the two spell books (mage and priest) different commanding attributes. Most games with magic kept it, Diablo ditched it. Some put it to good use: In the later Wizardry games, Intelligence determines the strength of the spells while Piety (as the other stat is called here) determines the number of spell points. Thus, a character with high INT and low PIE will be able to cast few, but powerful spells, a character with the attributes reversed will cast more, but weaker spells.
This is actually the only way split attributes for physical could make sense: if the second stat was actually endurance. After all, a 100 yard dash and a marathon require different kinds of fitness. Strength might go down after a number of combat rounds, this number determined by Endurance. But no game I ever played uses it like this. There are some games that have a fatigue or stamina system, but it is always a separate secondary stat (like mana or hit points) that depends on several primary attributes.
Incidentally, it is quite possible that the creators of D&D thought along these lines. After all, a character with low Strength and high Constitution can stay longer in battle unattended and will be more efficient against multiple weaker foes, while a character with the opposite stat combination will do better against a single strong foe. The original D&D rules are more abstractions than simulations, they were often taken to literal by the imitators.