I have created show and hide features in InDesign that I wish to export to Interactive PDF. These features work when viewed in Acrobat on Desktop, but not on iPad/tablets - why?

Why? Most likely because the PDF viewer on the tablet is too dumb to deal with show/hide features.

You might try PDF Expert by Readdle on the iOS devices, and qpdf Notes Pro on Android.

Depending on how the show/hide has been created when exporting from InDesign, it may work in those viewers. Otherwise, you'd have to open the PDFs in Acrobat and change the show/hide features to something more digestable by device PDF viewers.

BTW, you will encounter the same issues with the PDF viewing components in web browsers.

Hope this can help.