So, looking at the recent Zuma declarations on Dwilight, they gave no immediate reason for why they were doing it (then again, they're the Zuma, they probably don't need to). But a letter was circulated explaining from Terran's leadership as to what was going on - namely, this was a set-up.
From experience, reasons for war declarations are generally shared on the Rulers channel, and passed down to the nobility if appropriate. But I wonder whether adding some kind of field to the option to declare war would generate some political intrigue as well. Take the above situation - if the Zuma added the reason of "Terran (for example) plans to expand into our lands", then it could motivate players, or even realms, to mobilise. Or it may demotivate them to stay the hell away and let people fight. Then pick off the victor. As it would be transmitted with the declaration, the entire continent would see it.
There would need to be certain caveats to make it work. For a start, it would need to be short and sweet. Let rulers still send letters about the issue, pass them down if needs be. That way there are opportunities still for propaganda and spin. The next one would be whether the field would be mandatory or optional - something I'm not sure of. On the one hand, I don't believe any sane ruler would just put gobbledegook in the field, they'd put something meaningful. On the other hand, sometimes the reason may want to be kept quiet, or secret.
I do see one problem with such an addition though, and it's linked to IC immersion in a way. How would players, ICly, find out about the reason? Would it be rumours? Some kind of open declaration by the realm initiating hostilities? That's something that might need consideration as well as any other factors people bring up.
