“Why?” is also an ambiguous and lazy question.
When one is getting to know someone, there is usually a kind of carefully gauged trading of information. You say something light, they say something light, you say something slightly revealing, they respond with something also slightly revealing, and so forth. Maybe you aren’t being sensitive to the level of information trading. Perhaps they want to wait for you to say something vulnerable enough that they will feel comfortable saying something revealing too.
Also, as was noted, a whole lot of people simply don’t know why they prefer or don’t prefer something. The ‘why’ of that particular thing isn’t of interest to them. I like Stickley furniture. Why? Because it’s handcrafted and simple. Why do I like handcrafted and simple? Because blah blah blah highminded esoteric philosophy of the arts and crafts movement and the broader sociocultural reaction to the industrial revolution but really, I just prefer it. Taste is not a rational thing, ultimately.
I like tall pale guys with strong narrow noses, long knobbly fingers and dark hair. Why? I just do. I just came out that way. I can’t talk about the reason because there isn’t a one. It’s slightly irritating to be asked questions for which there is obviously no real answer. Especially when, as seems the case here, the questioner has a hard time letting it go.