with game mechanics as they are, there are a number of things.
Fixed, in-space assets - POS and stations, are things that wars actively threaten.
Mining is the only activity that can be really shut down by a war.
The rest of the time, then there are so many things that come into play, that a war can be rather pointless.
3rd party covops, 3rd party Guardians, 3rd party logistics and income. Alts, 2nd accounts, whatever. Intel, money, material is provided without any real payment, because who pays their alts?
E.g. Corp A has ships and isk provided by unknown Corp X. What would anyone have to gain by declaring against them?
With so many things to avoid consequences for those that know how to use them, then it means the opponents have to want to fight, have a reason to, inorder for there to be a war, instead of lots of evasion.
Unless they don't know all the means of evasion, in which case it's a war against the less competent, which could be a turkeyshoot rather than a war.
So... v0v.
Wars are good at being able to clear out POS that you don't want to be there, and against less skilled/crafty players. Against anyone/anything else, it could be an exercise in frustration and pointlessness. Who gets bored first, loses :\