Purpose of and best use for compile on iOS?

My wife has been using Scrivener on her iPad for her writing for a number of years and finds it quite useful and productive.

For my own writing needs, I have recently adopted using Scrivener 3 on macOS and Scivener 1.2.1 (2096) on my iPad. I am anticipating doing most of my writing on the iPad, syncing via Dropbox to allow for editing, etc. on the macOS machine. I even went to the trouble to create a custom compile format on the macOS device for PDF output format. I have no intention of not retaining access to a non-iPad device for the foreseeable future, so can easily do my compiling to other formats there.

However, this brings me to the crux of my question: what is the purpose of compile on iOS and how best to use it? Due to the nature of the writing (personal journaling), there are no predefined compile formats that would be appropriate for producing, say, a PDF version for review.