My response is what I have seen in practice.
We used to have a very robust social charity system. Now it is almost all replaced with legislated things tied in with welfare. If we had a UBI, it wouldn't exist at all. Any failure of people being fed will be look at as a problem of the UBI system, and the system will be demanded to fix it. (Which, in my opinion will never be close to 100%)
...people should have savings
HA!!! People should have savings now... and most live paycheck to paycheck.
You don't even want to know what people on welfare live like. (You have 25 days of food per month... what do you do those last 5 days?)
Yes, those people who work will have far more than those who don't. BUT, the problem that UBI is being brought up to fix is that people are being phased out of jobs. Robots are doing the manufacturing, so there isn't enough jobs for everyone. (in our current monetary system) So, if there is not enough jobs for everyone, telling someone to get a job or die... is telling them to die.
And thus, what is the use of the UBI in the first place?
The question isn't a matter of whether it is useful or works in all cases. The question is whether it is moral based upon first principles. Whether a UBI can feed someone or just amounts to $1 per day in purchasing power, it is a just system.
If people complain about the UBI not feeding people and attempt to morph it into a slavery system where the productive serve the unproductive then society will begin consuming its seed corn. Production will decline and the revised UBI will no longer be sufficient. The process will repeat until money is worthless and there is nothing left to divide.
The system I propose provides a UBI based upon first principles and does so without specifying the purchasing power the UBI would grant.
The biggest danger is people wanting to reinterpret their UBI as something it is not. Once they reinterpret it, then they will either start enslaving their fellow man or denying him his birthright. There is very little room to deviate from the 1 share per person per day without creating a system that is no longer sustainable or fair.