He's an ex for a reason

Are we required to have good reasons for all the decisions we made in our youth? I present the following conversation as an example:

me (referring to online pic of (now bald) ex-boyfriend with his new baby): I used to make out with that guy.
Joe: Why?
me: Dunno, seemed like a good idea at the time.

Also, I was about 15 when this happened. Besides the fact that I probably shouldn't have been making out with an 18-year-old when I was 15, am I expected to have a good answer for "why"?

• Because he was nice to me.
• Because 90210 was a repeat and I was bored.
• Because it was Tuesday.

Actually, those work just as well as the justifications I give for my actions now.

Joe: Why did you walk into that post?
me: Because it was there.
Joe: You didn't see it?
me: My eyes were closed.
Joe: While you're walking down the street?
me: The sun is bright.

Joe: Why did you use paprika instead of cinnamon on the toast?
me: Because it was dark.
Joe: Why didn't you turn the light on?
me: I'm conserving electricity like you're always talking about.

I don't understand why my reasons aren't good enough for him. He's hard to please, my husband...