This gets down to something that used to be a common UI design principle before software became so feature-ful it became impractical: manifest interface.
The idea of a manifest interface (which also is a principle in language and API design) is that if the software has a capability you should be able to see it. You shouldn't have to root around to stumble upon it. Tabs follow this principle; there's enough visual and behavioral cues to suggest that you need to click on a tab. The little "x" in the tab also follows this principle.
But context menus you access by right-clicking break this rule, which means that there may be millions of people laboriously clicking on "x" after "x", unaware that they can make all the extraneous tabs in their browser disappear with just two clicks.
This, by the way, is why Macintoshes were designed with one button on the mouse. But even Mac UI designers couldn't get by with just single and double-click, so you have option-click too, bit by in large you could operate most programs without it.
Anyhow, to make sure people know about this kind of feature, your program is going to have to watch their behavior and suggest they try right clicking. But that way lies Clippy...