Why don't you offer your own cloud sync solution?

2Do does not host your task data, because of the privacy and security responsibility that would carry. Instead it syncs through services you already have: your own iCloud account, Dropbox, iCloud CalDAV and other CalDAV servers, Todoist, Toodledo, and Apple Reminders. WebDAV sync is coming soon.

The iCloud method is worth a word here, because it is the one that feels most like "2Do's own sync". It is not. It uses the iCloud account already signed in on your device, so your tasks sit in your own Apple-hosted storage, private to your account, and 2Do keeps no copy of them anywhere. There is no 2Do server in the middle, no account to create with us, and nothing for us to read.

The trade-off is that sync goes through someone else's service rather than one tuned end to end for 2Do. In exchange, your data stays with the provider you chose. See Which sync method should I use? for the full list.