why everytime apple asks to verify payment details ??

hello,

i am using my same apple id in iphone 6 , macbook pro, ipad 4th gen and in ipod touch 2nd gen....

Many a times, i registered my apple id payment details and also provided card verification and $ 0.99 deducted everytime from my card account.
I have to use card verification as i often opt paid purchase in apps / games.
Now why the payment info not getting stored and then i will have to pay only d price of d app/service...

Kindly help me out, i am in a fix.....

thnx in advance...

Regards

Shuvajit m