So far as I am aware, there is no direct, word-of-god commentary on why Bluff, in particular, is found on the sorcerer skill list—see HeyICanChan’s excellent answer for what commentary is available, but note that it does not give reasoning for Bluff beyond saying it is what an internal R&D poll came up with. Both quoted WotC employees (Andy Collins and Sean K. Reynolds) express disagreement with Bluff being the sole Charisma-based skill on the sorcerer list, but offer no explanation for why others disagreed with adding more. Player’s Handbook, certainly, does not directly comment on it.
There are some hints at why Bluff might be a priority for sorcerers, however:
Some good sorcerers are driven by the need to prove themselves. Marked as different by their power, they seek to win a place in society and to prove themselves to others. Evil sorcerers, however, also feel themselves set apart from others—apart and above.
(Player’s Handbook pg. 51)
More often, however, sorcerers are on their own, feared by erstwhile friends and misunderstood by family.
(Player’s Handbook pg. 53)
In other words, there is an implied incentive to hide one’s sorcerous nature, which would require the Bluff skill to do.
But the problem with this argument is that there are similar implied needs for other skills not found on the sorcerer skill list:
Everything above that might justify Bluff could just as easily warrant skill in Disguise, but it is absent from the sorcerer skill list.
Other social skills:
Role: [...] Since a sorcerer often has a powerful presence that gives him a way with people, he may serve as the “face” for an adventuring party, negotiating, bargaining, and speaking for others.
(Player’s Handbook pg. 53)
I.e., Bluff makes total sense—it’s the lack of Diplomacy, Intimidate, and Sense Motive that makes zero sense. This line in Player’s Handbook only makes sense based on ability scores—high Charisma—but skill checks are, past the earliest levels, dominated by ranks, not ability score. This reads as though whoever wrote it either didn’t know the sorcerer’s class skill list, or misunderstood the ramifications of cross-class skill rank costs with respect to one’s ability to utilize a given skill.
Sorcerers create magic the way a poet creates poems,
(Player’s Handbook pg. 51, actually the first sentence of the sorcerer description)
Poets presumably use Perform here, which would imply sorcerers should have that skill. Though honestly, the correct skill to use for creating artistic works is a little unclear—Craft could make a case here—but that goes against the second half of the sentence, which reads “with inborn talent honed by practice,” suggesting that poets—along with sorcerers—do what they do more from Charisma than Intelligence.
Skills in general/more skill points
[Sorcerers] don’t have the background of arcane knowledge that most wizards have. However, they do have more time to learn
This sentence is an explanation of why sorcerers are proficient with all simple weapons, rather than the restricted list of weapons that wizards are proficient in, but it seems like it ought to also apply to skills—since their spells require less of their time, they should have more and more diverse skill sets beyond spellcasting. Instead, they get the same 2+Int that wizards do—and with vastly less benefit from a high Intelligence score.
In other words, the sorcerer skill list is dumb, and there isn’t really any good justification for it being the way it is. Contrast it with the binder (Tome of Magic) skill list: Bluff, Diplomacy, Gather Information, Intimidate, and Sense Motive are all on there (Disguise is again missing, though). And binders have far stronger explicit statements than sorcerers about being outcast and shunned,1 which might have justified an explicit focus on Bluff (and Disguise ⌐.⌐) over, say, Diplomacy.
So I heartily recommend bumping sorcerers up to 4+Int skill points per level, and adding at least Diplomacy, Intimidate, and Sense Motive to their skill list. Disguise and Perform also make a great deal of sense, though there is some argument that those skills tend to be a bit rarer on class skill list to make them a little “special”—I find this argument fairly weak, but it is true that these skills are less common. My games typically make these (and other) changes to sorcerers, and I have found them to be for the best.
- “the practice of pact magic is forbidden by most religions,” “[binders are often human,] but binders are no more welcome in human societies than any other,” “halfling communities [...] learn to fear them,” “elves and dwarves [...] tend to be [...] more opposed to binders,” “Others might misunderstand you,” “you can’t afford to be too open about your activities,” etc.