It isn’t though. Some already donate non-perishables they don’t sell to community food banks for the tax write-off. Running it yourself would just be an extension of that and would be a huge PR plus. I think if we made food donations equivalent to being able to write it off as an inventory loss they would be more likely to do it.
Afaik the reason they refuse to give away food in power outages is precisely that. If they have to trash it then it is a total loss and they can write it off at cost, if they donate it then only a portion of the value is counted.