There were several reasons for me to do it. But here is the main reason:
Local storage is not persistent. If space on your phone is scarce, it'll delete entries from local storage without notifying you (eg. http://gonehybrid.com/dont-assume-localstorage-will-always-w...). That shouldn't happen with desktop browsers since there is plenty of space available. So your data is more safe in desktop browsers.
Did you experience something else? Any suggestions on this topic?
Yotilo is not meant to be a full fledged timetracker. I'll publish a more complete project in the future with pretty good mobile- and offline-support.
Sorry, if you don't like it. I hope the reason above is understandable.