A box on a farm means much MORE handling of it, no? Currently no farmer I’ve met has ever handled pure ammonia, only UAN or nitrate/other dry solids. And like you said, they’d rather not. (although I also don’t know any who would drink glyphosates with how quickly they eat sprayers)
How does a box help with timing? Each farm must either store enough on site for an entire application (which farmers could already do if that was worth the cost) as it’s slowly generated, or they’re constrained by daily output of the box. Late shipments are bad, but a renewable only box running out on a cloudy week? No angry phone call to the coop fixes this.
Spreading the cost to centrally produce and store lots over many farms/industries seems optimal when one needs infrequent but huge quantities of anything.