Bullshit, cliche answers:
1). Because I love movies!
2). Because I have what it takes.
3). Because it "looks" fun.
4). Because it's been my passion ever since I was a child.
5). Because I want to be rich and famous.
Bullshit, cliche answers aside; answer these questions:
1). Are you willing to get rejected for the next 10-15 years and still be enthusiastic?
2). Are you willing to really give this your all? No bullshit excuses like; I have a full time job, or I'm a full time student, or whatever other excuses you use to justify throwing away a potential opportunity.
3). How would you rate (scale: 1-10) your networking skills? Also, are you a prompt communicator? Waiting hours (and some idiots wait days) to return emails and messages is a big NO NO! You have a mobile device; fucking use it!
I've met way too many people who are "passionate" filmmakers. But when it comes to actually doing the work, they're MIA!