MarkG:
Ok, that's fair enough, so it begs the question on why these boards that are from elsewhere are not simply labelled up as Arduino compatible?
Because, of course, they are being traded fraudulently. They are advertising that they are the quality-checked product manufactured under the Arduino control and whose sale supports Arduino development, which they simply are not at all.
MarkG:
And why doesn't Arduino allow the use of the name for that purpose?
It's called a trademark®. It distinguishes the genuine product from those who are not necessarily (and probably not) manufactured to the same quality standards and in neither past nor present contribute to the development.
Were Arduino to suffer others to use its trademark, its reputation for reliability would be impaired as a result of people's experience with the inferior products, to say nothing of its financial viability as a project.