Personally I think it's just courteous to put as much info as you can, but for example in wikicommons it will often say in parentheses that you're free to use it as long as you credit the author, so we should probably adapt accordingly.

Regarding education yes, I've found that legally it's a grey area when it comes to earning from it - whether you're a registered educational facility or whatnot. One of the areas I didn't want to start diving into in this post...