At companies with great cultures, employees are eager to show up and get things done because they genuinely care about the team and mission. That was very much my experience at early Google.
Companies with bad cultures try to motivate employees with fear and intimidation, or simply fail to motivate them at all, and everyone wastes their time playing video games or whatever. Not surprisingly, those rarely do well.
In my estimation, most startups have weak to poor culture, which is one reason why you read so many startup horror stories. My advice to anyone looking to join a startup it to pick a place where you are excited about showing up and contributing every day. I think that's a much better predictor of happiness and success than trying to follow the social media hype or hotness signals.