And yes, jazz and classical musicians rethink and reorient their musical paths, too. There's a whole long history of musicians entering the field via "straight" jazz and increasingly resisting not just the label but the sound -- and they do so in part by making music that sounds more and more like "everything else."
The modern version of that story is Glasper et al.
But on Dre: he has been nothing if not consistent in interviews for a long time now that he hasn't felt like making a rap album.
Considering he has, for equally as long or longer, not made a rap album... why don't people believe him? That's clearly not just a line.
So to answer your question: why not make the album he wants to make? If he has been struggling with finding the right output for his shit, and this actually clicked for him --- what reason does he need?