Thanks for saving me a click. Rene can provide useful information... but Apple definitely is afraid to cannibalize their products. There's no point in denying the obvious truth... any company that sells hardware does not want to cannibalize their own products.
Rather than arguing that Apple does not want the iPad to cannibalise the Mac, can it not be argued that Apple simply doesn't think that macOS makes sense on the iPad?
What I currently like about the iPad is that it is nothing like my iMac or MBA. Sure, there are some tasks that overlap, but for most part, each excels in its own area, and that's what I appreciate. When I am at home working on test papers and spreadsheets, I appreciate the 27" display of my iMac. When I am in the classroom, I am thankful for the ease of use and fluidity of iOS (which makes it extremely easy to handle on the go), the long battery life, and the 4g connectivity. I like being able to scan a document with scanner pro, then pass it along to notability without having to deal with a file manager.
I am using an iPad for work (and have been using it since 2012) precisely because it runs iOS, not macOS. Along the way, I find I am more comfortable working with iOS than macOS now. For the work I do, I for one do not want the heaviness of a legacy desktop OS weighing me down. The presence of the Mac is precisely what allows the iPad to be as light as it is - the iPad doesn't have to be able to perform certain niche tasks like terminal access because that's what the Mac is there for.
Having macOS on the iPad would very likely be a step back in usability for me. I have no desire for the two to ever converge, much less on the iPad.