I'm talking about jet fighters flying into another countries' airspace. What exactly are you talking about?
Necessary: required to be done, achieved, or present; needed; essential
Sorry, couldn't resist. How about war? That seems like a good requirement to me.
There's a good old way to explain (or rather show) the complexity of programming to a computer newbie. It's called "playing the robot". The idea is that the one doing the explaining agrees to "follow orders" (can be on paper for all it matters) but then starts questioning each and ever order to the details that look stupid and excessive in the eyes of human intuition. Let me continue the example.
Ok, on second though... let's not. Let's take a shortcut...
Required for what?
Is crossing borders to scout "necessary"?
Is it "necessary" to cross them to settle on the other side of them faster?
Is it ever necessary to settle?
Is it necessary to win?
What is necessary FOR wining?
Is it necessary for me to ask any more of these question to make it clear that necessity is excessively subjective?
Your culture isn't your borders. Space is vast. Your borders encompass the atmospheric bubble around your colonized planets.
And yes, the AI gets annoyed when you fly through their space. Just like you get annoyed when they fly through yours. Huh. How about that.
So, you've got me wondering... are you troll-fishing or are you just posting while drunk?
Borders on earth aren't much more "material" than empty space. The concept of borders involves the claims to territory, rules of crossing, jurisdiction and the ability to enforce those rules by actions that are "allowed" by the aforementioned jurisdiction. Basically it's a statement "don't get on my lawn or else" + a statement "this here is my lawn" + a law that will pardon you if you harm a trespasser (in certain law-defined ways) while he is on your lawn.
That last part is something that we lack.
Also, NO the AI doesn't get annoyed. And unless SD can pull GC race out of the lore and into their office there'll be no such thing as AI that can get annoyed. All they do is show you a red minus and use that to evaluate their reactions to you. The player on contrary CAN get annoyed and doesn't like it. On top of it he cannot scare the lawn trespasser with big bad red minus of negative diplomacy. Which is bad because that means that as far as AI is concerned - we're totally ok with him waltzing through our territory.
Ah heck, why am I even bothering to reply... you obviously aren't taking it seriously.