Why don't you ask them? There could be lots of reasons. For example, things may have happened in their personal lives while you were away, things that are occupying their thoughts and setting their moods. Or they may want to experience some of the places you've been for themselves, and don't want to "spoil" the surprises (some people are like that). Or they may simply be on the miserable git spectrum and, like some on this thread, happy to admit it - personally, I'd be interested whether you had a nice time but horrified at the idea of going through your holiday snaps at work!!! That's just alien to me ... the very idea that you would even bring them in for me to look at. People are different, is the point.
> Small minded people, this is all I can think.
That could be very harsh. For example, look at this story on the BBC today -
https://www.bbc.co.uk/news/blogs-trending-45558344 - it's a great example of how knowing the other person's situation can help you to see their actions in a different light.