An educational point is also a very personal POV.
When I go to a zoo, I have minimal interest in this, maybe for some favorite animals..
To give a personal POV: I'm an amateurphotographer and I visit zoos with different intentions than others. (no love for photographers in this game

)
Maybe it's something local..
I regularly visit zoos in the Netherlands and sometimes Germany and you sometimes see the occasional zoo keeper (not that much though) but rarely seen people ask them questions. (school trips excluded). Also the staff buildings are well hidden (most times). I've been to the workshop/maintenance shack of our local zoo, it's definately not close to the visitors route.
Even when it's feeding time, most people just enjoy looking at the animals react to feeding time (wish that feature was present in the game).
In most zoos the keepers don't stick around for questions, they just give a 'show' at a specified time.
But if you ask them, they'll most likely be happy to answer the questions.
I'm not saying there aren't people who aren't interested.. (offcourse not) There are just 2 sides to this 'negative impact circle'..
But a workshop ? and a staffroom ? I don't think people would want to see/hear/smell that between 2 exhibits.
Agreed. being upset about it is a bit too much.