Taken from the bankrate.com website:

10 Less stress because you're organized.

9 No more expensive late fees.

8 You'll improve your credit scores.

7 Better interest rates come your way.

6 Less reasons to argue, so personal relationships improve.

5 You feel more financially secure.

4 Your finances are more durable.

3 It helps build personal wealth.

2 No more guilty feelings when you splurge.

1 You realize true financial freedom.

Another that I would like to add is: Setting a good financial example

for your children (a priceless gift)

Anyone care to add their own reasons?