Buffout is a highly advanced steroid that was popularized before the Great War by professional athletes and their clandestine use of the drug.
Due to the wide SPECIAL stat increases Buffout provides, anyone can really take advantage of using Buffout simply to increase skills. However, the extra Strength or Endurance does not provide extra health.
Ironically, hand-to-hand focused fighters may see the least benefit, as while they gain a small damage bonus and a similar accuracy bonus, some ranged skills get disproportionate bonuses from Agility (both Throwing and Unarmed get +4% from each Agility).
Regardless, characters whose relevant skills are already high will have a greater benefit from using Buffout, as gaining even just 2 points in an untagged Melee or Unarmed skill at 150% is equivalent to 6 skill points. This is even greater for Small Guns or Throwing, especially if either is tagged. While Buffout will not transform a weak fighter into a fighting machine, a single or double dose can amplify an already skilled combatant.
After Jet, Buffout is the next most common chem for much of the game. However, Buffout is still rather expensive and rare until the player reaches New Reno, or even San Francisco, so this says much more about Jet's prevalence than Buffout's.