Law regarding Night outs

I have few friends, who stay at a rented accommodation. Which means they don't have any interference of any kind, so the other day one of my friends was standing road side with her boy friend, the time she told me was 11:30pm. Some police men found them and started asking questions about what they were doing and their indentities. The girl was asked to go back to her PG (which was near by) the guy was taken by police to a police station for questioning. Later few police men came to my friend's PG, and asked her few questions like what were they doing so late? She answered that they were just chatting, which they were actually. Police men asked her to call her parents. For reason which i don't understand. They wanted her parents to know about this. My friend is 24. She wasn't doing anything wrong. Can a police arrest someone for just standing roadside and talking? Without any warning or any suspected incident, can they take us away? Or can they at any point just ask us to call our parents? I mean we can call our friends, siblings, but why parents? Now before you judge me, i understand it's not safe to be on road like this and it's a good thing to do, but does it mean that i have to go to police station or call my dad? I'm an adult, and i earn my own bread, pay my own rent, drive my own vehicle, how can a police man ask me to go police station for just standing on road?