It's well established. Most public websites for museums have galleries of high res scans, and they're mostly all trying to keep you from downloading it. There are lots of tools out there to circumvent them, however.
This is a tautology and one at odds with itself. They simultaneously provide the high res scans but you think there’s a conspiracy to keep you from them. Why provide them in the first place then?
Not at all. They want people to experience what they have, but they don't want a small subset of people selling prints, T-shirts, and little statues. From their perspective, they sell excellent quality prints, etc. in the gift shop and online, and the proceeds benefit the collection. So they lock down downloads if they can.