In addition to what others have said, I think it is important to consider that government retirement assistance (whatever it is called in each instance) is basically a promise that can be revoked. I talked to a retired friend of mine just yesterday and we got onto that subject; she mentioned that when she was young, the promise was for 90% of one's pay, paid by the government after retiring. It is very different today.
Yes, you can gamble that you won't need the saved money, and thus decide not to save anything. What then if you do end up needing the money you did not set aside, but rather spent?
You are just now graduating college, and assuming of course that you get a decently-paying job, are likely going to have loads more money than you are used to. If you make an agreement with yourself to set aside even just 10-15% of the difference in income right from the start, that is going to grow into a pretty sizable nest egg by the time you approach retirement age. Then, you will have the option of continuing to work (maybe part-time) or quitting in a way you would not have had otherwise.
Now I'm going to pull numbers out of thin air, but suppose that you currently have $1000/month net, before expenses, and can get a job that pays $1800/month net starting out. 10-15% of the difference means you'll be saving around $100/month for retirement. In 35 years, assuming no return on investment (pessimistic, but works if returns match inflation) and no pay rises, that will still be over $40K. That's somewhere on the order of $150/month added to your retirement income for 25 years. Multiply with whatever inflation rate you think is likely if you prefer nominal values. It becomes even more noticable if you save a significant fraction of the additional pay; if you save 1/3 of the additional money (note that you still effectively get a 50% raise compared to what you have been living on before), that gives you a net income of $1500/month instead of $1800 ($500/month more rather than $800/month more) which grows into about $110K in 35 years assuming no return on investment. Nearly $400 per month for 25 years. $100 per week is hardly chump change in retirement, and it is still quite realistic for most people to save 30% of the money they did not have before.