Latency. Not all engineering tasks are based on static data.

Tools. Few easily allow you to farm out your simulations. Many tools have decades of development in them. You could in theory develop them for tablets, but there's not been a good business case for that.

You will be able to do that kind of work on something running iOS (or its successor) in 5 years.

Mechanical, civil, aeronautical engineering, these fields are notoriously slow at adopting the latest and greatest technology. A lot of our code is still written in Fortran, and C++ libraries might as well be considered state-of-the-art. Further, when you're doing a lot of work on code, you are also multitasking like nobody's business. I have three screens, one for code, another for documentation or something, and a third for my browser (for example). iOS specifically will need massively more multitasking capabilities, a proper filesystem, the actual ports of software like CATIA/ANSYS, USB ports etc. to even become part of the conversation. Not to mention the fact that I just don't see why an ipad would be useful in this context. I'm not constantly moving between offices, or from my home to office, as I do advanced simulations. My workstation stays plugged in, and so the ipad doesn't solve any existing problems for me.

As a final note, these fields are involved in most things that you and I use on a day to day basis, so it would also not be right to call them an outdated niche that can be neglected (not that you are calling them that).