What time is it now?

Two men in the train. One is about 25, another is about 50. The young man asks:
- Could you please tell me what time it is now?
The old man keeps silence. When the train arrived the old man says:
- It is half past six.
The young man asks:
- Why didn't you tell me when I asked?
The old man explains:
- If I told you the time, you would thank me. I would ask you where you were going. You would tell me that you don't know anyone in this town. I would invite you to my house. You would see my daughter, fall in love with her and want to marry her.
- So what?
- Why should I need a son-in-law that doesn't have watches?