In a puritanical society, vice by nature is a counter-cultural act. Especially when in one of the most hegemonic societies on earth consider sex to be the greatest taboo. This counter-culture creates a culture of pushing boundaries and exploring the unsaid in polite society.

In many cases, like how one would expose a more emotional an vulnerable verison of themselves via kink and sex. The lack of inhibitions may lead one to exposing their social and political values as well. Whether it is egalitarian equality (e.g. a lack and blending of social roles regardless of social or political identity); or an enforced heirarchy (i.e. that denegrate and or subjugate certain social and political identities).

Most porn does sits somewhere far more moderate, in-line with social values in mainstream society; monogamous and conventional man-on-woman sex where the man is a strong actor while the woman is a to be obtained and ogled.. But just because it's "morderate" does not mean it does not have a political perspective and message. Just like how many major Hollywood movies perpetuate mainstream American values by portraying them uncritically (e.g. "police and military are necessary if flawed institutions", "the highest virtue to be an individual fighting against a world that is against you", and "wealth and prestige are good and valuable things to have, up until you become an asshole."). Typical pornography uncritically accepts and portrays mainstream values and perpetuates them; especially since it is in an uninhibited.

Not to say that mainstream values are necessarily bad or need to be critically attacked or subverted in any and all media (including pornography); but merely an explanation of how porn is a social and political frontier.

There's still the question of the objectification of women.