It's not necessarily selfish. One argument I've heard against life extension is that if it is only - or even deferentially - available to the upper stratum, the power of compound interest will allow them to accumulate and hold even greater proportions of social and economic resources (esp. zero-sum resources like status and power). Others caution that social structures will become more resistant to change if those with the most social capital are also the longest-lived. Most people really do care about status relative to their contemporaries-not just absolute status - and how it affects their agency. And then there are environmentalists who have ecological worries, and others with different specific but impersonal concerns.

Death is a great redistributor for all forms of capital - social, economic, and organic.

I can think of counter-arguments to these points, but they do not necessarily stem from selfishness,merely different preferences.