It probably wouldn't generate very much revenue - it's a banner you generally see briefly at a poor angle in the middle of a crowded picture, with relatively low resolution, and limited guarantees that it was actually shown to anyone at all (as opposed to being displayed in the instance when they happened to be looking the other way), with no ability to click-through to the actual product web page? Who's going to pay for that nowadays? "Not amazingly invasive" is generally called "worthless" in marketer circles, I think.
If it's not intrusive enough to get people to play X4 instead, no-one's going to pay Frontier any measurable amount of money to put it in Elite Dangerous.