FRien said:
From a foreigner perspective, that one kinda makes sense. If something you love is destroyed, rebuild it, but stronger.
It wasn't something loved, it was just a pair of towers. What made it so important was the devastation and casualties. Rebuilding the towers would have meant building on top of thousands of graves, would have meant building over all the memorials erected for lost loved ones. People involved in the incident that survived are still feeling the effects today. Too many people would feel an attempt to rebuild the towers to be disrespectful both to those that died and to those that survived.
I know no one outside the US cares about that event, but I would hope at least that much to be understandable.