Dear Bhaskar,
I agree with the view points of Mr. M.V. Kannan.
To add further, Organization will have the justification for increasing the notice period purely on account of its business interest as always there will be a knowledge loss once a person is moved out. Though the vaccum can not be filled immediately with a new person, yet some knowledge can be transferred within such notice period. With this view in mind, certain organization has extended its notice period even as 90 days. However, allowing the individual to serve full notice period is totally rests with the position and responsibility the individual has been holding coupled with the sincerity of that person towards the organization. In contradiction to this, there is a belief (not in all cases) that once the person is resigned the 'loyalty'/ 'sincerity' towards the organization + the output gets diminished and the individual starts flashing sorts of negativity towards the organization among colleagues. Therefore, majority of the corporates, in the current scenario, believe in relieving the resigned employee immediately by waiving off the notice period, if they feel that there wouldn't be much value addition by holding such outgoing person.
Further, certain organization (owner dominated) has the tendency to hold people for one reason or the other only to harass the outgoing person.
All the above 3 scenario are of pro-organization and as such, I would also suggest you to speak to your HR and request for waiver on account of your marriage, which, I am sure, will be acceded to. However, as suggested by Mr. Kannan, you may pay the notice if you have ample money. (Any way you are going to spend money on your marriage!).
All the best,