Introverts are always there when you need them, but they also need space. You see.. they listen, they care, they empathize. When they give, they give like a candle burning from both sides. But there's a limit. They're human. They're there, just let them catch a breath.
Introverts don't lack social skills, they're just not interested. They can talk. But not with everyone. They need the right mood, the right place, the right person. They need to feel your vibe and trust you. Then, they talk.