Why are womem not allowed to drive in Saudi Arabia?

Firstly: It is well-known that it is not 'Haram' in Islam for women to drive. In fact, Saudi Arabia is the only Muslim country in the whole world where this unique situation seems to be imposed. The Basic Law of Saudi Arabia states that the Quran is the constitution of the country and that the Kingdom is to be governed on the basis of Islamic Law (Sharia) and Islam is not against women driving as far as they in veil.
Secondly, It's not even against the society norms, Infact I saw this interview of King Abdullah, where is supported Women to driving ( can't find it online now) there is a possibility of..

- A large number of people are still conservative and wud not like if this ban is lifts up and as per King Abdulalah's words, he doesn't want to do anything that is not acceptable by his people.
- Men insecurity, yeah, in a society where number of female graduates is bigger than males, insecurity wud automatically comes.
- Believe it or not, saudi arabia is not as shareef as you think, the youth is too westernized and they fear if they allow females to drive, things will get out of control.

I personally think, driving is not an adventure or luxury, its a need of today and women here shud be allowed to drive. Well, things are changing ..so, lets see what happens..

EDITED
Saudi woman 'spared lashing' in driving case:-
<http://english.aljazeera.net/news/middleeast/2011/09/201192820341050915.html?utm_content=automateplus&utm_campaign=Trial6&utm_source=SocialFlow&utm_term=tweets&utm_medium=MasterAccount>
See, how rapidly things are changing here :)

Its the part of their constitution I guess.

Because they fear that women will misuse this right which is illogical and shows insecurity of Saudi men =P

Actually, women are not allowed to go out on their own and need to have a 'mahram' with them at all times when they are travelling, in Islam...and since once women are allowed to drive this law is very likely to be broken more often therefore it is not allowed... Furthermore, it increases the chances of women harassment if it is allowed...besides who needs to drive a car if you have a mahram with you who can....and don't go on about some hypothetical situation where that wouldn't be possible because laws are not based on exceptions...