Besides the ones you always hear. In other words, reasons that don't have to do with terrorism or national security. It's worse now, but even when I was studying Arabic in the mid 90s it was always assumed it was related to terrorism or security.
1. It's unique, especially if you can tell people you're not studying it to become a terrorism expert.
2. It's interesting. I love the grammatical system of Arabic and it's always worth learning a language to see how another group of people looks at the world.
3. Business. Yes, even though you only hear about terrorism in Arab countries, there are business opportunities there just like there are in China or Sweden or any other place.
4. To learn more about Islam. No matter where in the world you go, if you know some Arabic, you'll be able to make connections with Muslims even if their native language isn't Arabic (and it isn't for most Muslims). Unquestionably if you want to do anything with Islam, study Arabic.
5. But the main reason I studied Arabic (and any other language) is that it opens up communication with millions more people. Non-verbal communication stories are great, but it's just not the same. Arabic is the 5th most common language in the world. That's a lot of interesting people to talk to.