Social skills in Neverwinter Nights

Generally, the potential benefit of social skills is determined by the designer(s) of the environment that you are venturing through whether it is content created by the Bioware staff or the community at large.

Persuade is the most common skill check used in convos. It can serve as a "shortcut" path towards a toon achieving a goal, often by bypassing combat and sometimes to gain information or items that would otherwise be unobtainable. Occasionally, it can be used to shift your toon's alignment. Bluff is used in a similar fashion. When convos focus on social interactions, they can offer multiple check opportunities so usually only one skill is worth boosting, if at all.

Intimidate is unique in that it serves multiple purposes. The social aspects, of course, but also as a prereq for Weapon Master and to affect the DC of the Terrifying Rage feat.

Fortunately, none of these skills require training so oft times, just boosting your CHA via gear and/or buffs is enough to win the related skill checks. Classes that focus on CHA like bard and sorc typically have the most to gain by a modest investment in those skills because they are empowered to win the toughest checks. Some races are poorly suited by their intrinsic bias, like half-orcs and dwarves. If you want to build a charismatic character to deal best with the NPC community, choose one that is not penalized by virtue of their heredity.

The bottom line answer to your question is, unfortunately, that you really won't know until you have played through at least a portion of the module/campaign whether social checks have been implemented. It is quite common for players to create a "test toon" based on a very diverse skill set (like a rogue or bard) just to get a feel for their surroundings before venturing in earnest.