very interesting points put forward...perhaps one of the most refreshing threads currently...
My top 10 reasons presently

are :
1. Accelerated Growth..moneywise as well as an opportunity to do what one likes ...maybe research for some,marketing for others etc etc
2. More responsibilites,more intellectual involvement and stimulation and more interaction with others because of the nature of a managerial job which an MBA course leads to
3. An opportunity to diversify/explore other areas and learn about the various aspects of an industry and its functioning and also dicover one's own self in the process as was pointed out by chopsuey and others...
4. A Masters qualification under your belt ==> feel good factor

as well as an enhanced CV
5. An opportunity to be a student again..and this time by choice

...opportunity to sharpen learning,teamwork and many other skills as well
6. As reaching a point of decision making is inevitable in any industry(and in life 2), MBA if pursued in an open minded and sincere manner would help one become more efficient and effective as a person and at the job....an opportunity to master the theory of management so as to make better decisions tomorrow
7. Partial discontentment with the current IT job because of an acute lack of sustained interest in tech stuff and it doesnt pay that well too
8. "Because its there" factor...... the MBA competition infuses life with some enthu,some challenge,some excitement,something to strive for...without which maybe life might have been less exciting

9. An opportunity to network,make new friends and acquaintances and learn from, and view perspectives from the talented and hardworking peer groups' point of view
10. Money again..
Would like to quote something I had heard in a movie,where the father tells his son "You've got to do what you have to do in order to get what you want to do"..What is it that we want to do?? and what is it that we have to do in order to get it??The answers vary but I am sure many of us like making a difference, financial security,pursuing our hobbies and interests, taking care and helping out our loved one's,peace of mind, maximizing our own potential....the feeling that we experience in the process is what might be called happiness...I dont think its an exaggeration if I say that money could be a possible solution for many of the points listed above provided we manage it well...being an idealist myself,I have learnt quite late that money is not the problem,its how we intend to use it and whether it fits into our broader scheme of things..money is,in my opinion the monetization of the amount of value we are bringing in {luck adjusted :)}(from the payers perspective).... Also while it is worthy to quote and idealize Howard Roark etc etc one cannot ignore the disparity in the contexts of the two societies,the needs,the family expectations and bonds,liabilities,education loans,house loans,health costs etc etc in our society are different......and also remember that Howard Roark was supremely gifted to begin with