Improvements in welfare occur when there are improvements in utility, and those occur only when an individual gets an option that wasn’t previously available. We typically prove that someone’s welfare has increased when the person has an increased set of choices.
When we make that assumption (which is hotly contested by some people, especially psychologists), we essentially assume that the fundamental objective of public policy is to increase freedom of choice.
I will leave it to others to dispute the notion that more choices are always better than fewer. But I can't help but think that it is to easy for those of us who are tenured professors to extoll the virtue of free choice, for the simple reason that we get so many, well, choices. We get to choose what we write, we to a large extent get to choose what we teach inside our classes, and we can piss our deans off and pay fairly little in the way of consequences. We might not get a raise or we might have to teach a class that we would rather not, but this is all small beer. We can make an awful lot of choices and still be economically secure.
Now consider the administrative assistant at a corporation who has a boorish boss and a sick kid. The company she (he) works for has a good health insurance plan, but if she were to leave, she would find herself unable to get coverage at a reasonable price. Does she really have choice?
Consider the West Virginia coal miner who goes into a dangerous mine every day, and whose life expectancy is shortened with each hour worked underground. Now consider the fact that the miner grew up in a West Virginia town with a poor school in an environment where going to college was a rare phenomenon. Does that miner have a choice?
I could go on, but I think the point is fairly clear. There are times when government intervention could expand the choice set up a large number of people.
Ed does point out how government can improve choice sets, and for that he deserves credit. But the more fundamental problem is that market economies produce large institutions that have limited markets inside of them, and therefore sometimes have hierarchies that can be as inhospitable to personal liberty as government bureaucracies. Elinor Ostrom's Nobel win in 2009 shows that the economics profession is beginning to recognize this problem, but I am not sure Ph.D. students are broadly encouraged to study it.