For science experiments and infrastructure this makes a lot of sense: we need to tell tax payers why we're taking their money. I'm a bit sad that it's not more widespread for a lot of critical infrastructure e.g. ferries, power plants, factories, etc: it's a great way to get people interested in engineering and big cool public projects.
It's often worth asking, the reactions can vary a lot. For example taking a ferry, I like to poke around and see how everything works:
- In Long Island Sound, even without going through any doors I got someone asking why I'm interested and essentially telling me there's no way in hell I could e.g. see the engine. He seemed to be 5 seconds away from calling the police.
- In Stockholm the engine mechanic noticed me looking around, invited me to climb down the ladder into the engine room, and showed me how everything worked. It was one of the highlights of that trip.