I've always found it difficult to talk about, e.g. food. "Isn't this food great?" "Yeah, it's delicious"! Similarly with the weather, or any other conversation where you're basically just repeating what's obvious to both of you.
Of course some people prefer it this way, and genuinely enjoy small talk -- they don't feel a need to be talking "about something". Far be it from me to piss on their parade. But if you don't understand this need, consider yourself lucky.