To add to Jayde Moon's post, remember that NPCs are people, and they have agendas. Just as being good at weapons and combat doesn't mean you'll always be successful in combat, being good in social skills and graces doesn't mean you will always get your way with people, even if you succeed in making them like you.
I remember once I was running a d20 Star Wars game, and one of my players made a female Zeltran. A Zeltran is an alien that emits pheromones and is usually pretty handsome. His idea was to achieve all the effects of a Jedi Mind Trick, but with sheer Charisma. And he went full slut with this character, to the point it got really disturbing that the other players had to intervene on her behalf because there is an actual insanity called Nymphomania.
Generally, it worked where she encountered humanoid males that looked reasonably human (humans, zabraks, chiss, etc.). And it worked with females too. She was able to get transportation free of charge (well, without credits, anyway), ask crime bosses to hide her and her companions, get equipment at much lower prices, and so on. Where she ran into roadblocks was where NPCs had bigger agendas going on. For instance, I had an Imperial Commander who was hell-bent for leather to eradicate a Rebel cell over a world, and if he failed, he'd have to apologize to Darth Vader. A few of the PCs, including the Zeltran girl, was captured, and the Zeltran succeeded in seducing the commander, but only that the commander was willing to let her live and be with him, but the others were going to be handed over to the executioner. This forced her to rely on skills that her player really didn't concentrate on, such as stealth and computer use skills so that she could escape from the commander's quarters, distract the guards attention, and help her companions escape custody.
So there are always limits to how powerful such abilities are. In fact, when she tried to distract the guards, she still had to draw a blaster to kill them once the other PCs had escaped. Because no matter how pretty someone is, that can't trump strong agendas.