I'd go with either 1) or 3), but lean towards 1) based on his track record. Notwithstanding his pleas of innocence and the debate over whether staying off the mound is even a real thing, A-Roid has been playing ball practically since he could walk and has been a professional baseball player for literally half his life (also literally his entire adult life). The suggestion that he's never heard of such a thing or that it has never occurred to him strikes me as some serious bullshit in the same way that all his other claims of innocence sound more like bullshit every time he has to explain another action. It's chintzy and bush-league, but if it gets into the pitcher's head just a little, he's accomplished his goal. But, to give him the benefit of the doubt, there is the possibility that 3) is true and that he just lives his life completely oblivious to everything (and everyone) around him. Big egos tend to have that effect on people.
I think there are two reasons. The first one is that pitchers in the modern era, for most part, are a bunch of pussies and that is at least partly due to the use of aluminum bats in the lower levels. Used to be that you could challenge a hitter with a pitch in on the hands and saw his bat in two; when the batter is swinging aluminum, that inside pitch can be fought off for a basehit. As a result, the art of coming inside on hitters has largely been lost on pitchers. Additionally, because any idiot with an aluminum bat can hit a fastball, more and more emphasis has been placed on throwing wiggly stuff, and so kids don't develop the velocity they once had on their fastball. Moreover, it has made hitters more aggressive about crowding the plate because they don't fear getting hit as much. And because the net result is fewer hit batters and pitchers getting used to being abused by hitters with several huge advantages, they don't tend to take out their frustration on the hitters' ribs anymore.
The second reason is money. With so many dollars on the line now in the pro ranks, a lot of pitchers are reluctant to dot a hitter with a purpose pitch and hitters are far more likely to charge the mound if they do get hit, rather than just taking it like a man and going to first base. Every now and then you'll see a remoresless power pitcher out there with no qualms about knocking people down (see Nolan Ryan, Pedro Martinez, Roger Clemens, etc.), but it has become pretty uncommon to take care of your own business. I firmly believe that's to the detriment of the game -- getting hit by pitches now and then is part of baseball -- but it's probably something that will become less and less common as time goes on.