Probably a license issue
There is a version of OpenOffice for iOS. It is full-fat, does everything the desktop version does, within the limits of a touch rather than GUI device. There is a ‘reader’ version of LibreOffice for iOS. As of the last version I tried, it is much more limited than the OpenOffice port. From the weaseling in the product description, l suspect a problem with the license, which means that the LibreOffice reader is crippled on iOS and probably can’t ever be fixed. Not unless LO changes licenses, something I expect will happen at around the same time as Satan goes ice-skating.
Warning: both versions are ad-supported; the ads in the LO app are incredibly annoying and can’t be turned off, or at least I didn’t work out how to turn them off before wiping the app from my system, while the ads in the OO app are less annoying (hard to be as annoying) and can be turned off by a suitable payment. That got killed on my systems too, I just don’t feel like being subject to ads to use an office suite, and I’m not paying one penny when both Apple and Microsoft supply free, no ads, office suites for iOS which work adequately. At least they work well enough for my needs. Others may differ.
The devs behind the LO ‘reader’ make a big deal of not being affiliated with either LO or OO, but can ‘read’ documents from both. (Gee. Really? Who’d have thunk it?) The devs behind the OO app are less prominent about not actually being OpenOffice, even if searching for ‘Apache OpenOffice’ in the App Store leads directly to their app and offerings from Apache itself are notably missing.
As usual, the major enemy of open source projects are the licensing and the egos of the devs. It means that those of us who just want to get work done use closed-source apps, because they mostly work and are actually available. If the actual devs behind OO and LO put versions on the App Store I feel sure that they would be better. And no ads anywhere. They won’t, and never will. Somehow VLC manages, but not OO or LO. Sigh.