Why should I keep unlimited data?

Hello! Recently I've been looking at ways to trim down costs and by happenstance I was checking my account when presented with the option to change my plan from an AT&T Unlimited data (grandfathered since 2008, $160) to a mobileshare plan (two devices, 10GB, $130). The combined typical usage from both lines tends to be about 2.25 GB a month on LTE iPhones. Other than the typical future-proofing argument, why should I keep the unlimited data plan when I can trade it for something that will save me over $300 a year and have a buffer over 400% of what I use (and have been using)? I would love to hear any reasons you can think of (new technology, etc) Thanks