Siege camps are still a counter to traps. Just not to the extent that "why did you bother building a trap?".Nothing is being done to make city building a priority, all that is happening is a hammer is coming down on free hits, but in a completely unbalanced fashion. Now there is no counter to traps and they will likely reign supreme until that is addressed a couple more years from now.
Normal Sector: 100% attrition.
Fully Trapped Sector: 200% attrition.
Fully Sieged Sector: 33% attrition.
Fully Trapped and Sieged Sector: 66% attrition.
If anything this balances out the (potential) usage of traps and sieges as opposed to only sieges.