It seems to me that when declaring war in Stellaris, there is little reason not to set everything you possibly can as a war goal: even if your actual strategic goals are quite modest, you can just select the goals you actually want when negotiating peace, and if you managed to rack up more warscore than you expected, then possibly you can get some "bonuses" you didn't originally intend to get, provided that you put them in your wargoals originally.
Is there some mechanic I'm overlooking that would encourage you to exercise the slightest bit of restraint in setting initial war goals?
Best Answer
I think it's a dormant feature to provide a more detailled warscore calculation at some point. E.g. not fulfilled wargoals could provide negative warscore for you. So taking too many goals would seriously hinder your potential at winning the war.
However as it is currently is, there really is no reason not to select as many war goals as possible.
With Stellaris next expansion revamping warfare massively, we may see some changes.