Besides having to wait for the installation, one important recurring inconvenience for me (on iOS) is the lack of autofill. Especially autofilled user names and passwords.
I really wish Apple would add a password-manager extension point to iOS. Since they're trying to push iCloud Keychain I'm not optimistic about this happening, but it would be a really nice way to make password managers more attractive.
Maybe it's just specific apps integrating with 1Password, but Mint, among other apps, already can do this (and it brings up what appears to be an iOS share sheet). But this feature has largely become irrelevant to me thanks to almost every app I use that requires sign-in supporting Touch ID.
> I really wish Apple would add a password-manager extension point to iOS.
They kinda have in 2 ways - as of iOS 9 or 10 your app can utilize login credentials from your web domain name if certain requirements are met, and there's touchID for instant login after the first authentication.