On my phone it's really not a big deal, since the data consumption is minimal. But I like to do longform reading on my Nexus 7, which is a wi-fi only model, and the places where I'm liable to sit around for an hour (i.e. the doctor's office, the gym, a lo-fi coffee shop, etc.) usually don't have accessible wi-fi. The ability for the tablet to sync with Pocket while it's on wifi and have everything cached when I'm off is extremely useful.