This reminds me of something that I heard once from a Chinese teacher. I can't vouch for the accuracy of it, but he was definitely on to something : In the West, it is assumed that it is the speaker's job to make himself understood to his listeners. In the East, it is the other way around. In recent times, it seems like we've gotten even more extreme. The speaker or writer must not only spoon-feed the understanding,…
An example of unnecessary effort would be using a foreign language listeners have no particular interest in learning. Personally, I would rather have my math class in a language I am at least fluent it, so that I can focus my attention on the math and not on the language. I also like my teach when they have an understanding of the psychology of learning, so that I can learn more effectively. Entertainment and motivation is part of it. It is spoon-feeding, but that's also how you get people to focus on the heart of the matter.
At higher levels, it becomes less of a consideration, not because it is unimportant, but because at high level, knowledge itself becomes scarce, so you'd be lucky to find someone who really knows his stuff, even if he isn't the best at making it easy for people to understand. So the listen can spare some effort as it is the only way to get that knowledge.
In the old days, knowledge in general was scarce so it made sense to tip the balance in favor of the speaker as you'd be lucky to have a knowledgeable speaker at all. But now, almost everything is a few clicks away on the internet, and the entire point of having a speaker is to present the information is an easily digestible manner. If you want to go "the hard way" you can do it by yourself, papers, textbooks, etc... are everywhere on almost every subject at almost every level, even more so if you embrace piracy.
As for painting, or meaningful art in general, it is also part of the artist job to guide the viewer, not just dump a random idea on canvas, this is just lazy (on the part of the artist). Leave some clues leading to the big idea. Think like a puzzle. Puzzles are designed to be challenging, but they also involve guiding the player so that in the end, they can solve a more difficult challenge than they would have been able to with no help.
Another thing to consider is that in a speaker-listener relationship, there are usually more listeners than there are speakers, so it is more efficient to have the speaker spend the effort being understood than having the listeners spend it understanding.