They are super wanted but it's true that it's very hard to get into.

Want to learn Windows, Linux, cloud whatever? Just build a cheap home lab and play to your heart's content. Because really, training is not how you get good. Nor is certification. It's the hands on experience that comes from running into the crap the vendor doesn't want to tell you. All the little annoying flaws they keep out of the documentation under pressure from marketing.

Good luck doing that with a system Z. Try to find one on eBay for peanuts the way you can get a nice ESXi server.