2) A perception as "natural", together with the naturalistic fallacy. The black plague and cancer are "natural" too, but we have no qualms eradicating them; yet for some reason, people romanticize death, especially when thinking primarily about it applying to other people rather than themselves.

3) Related to that naturalistic fallacy, aging afflicts a less sympathetic group. Given a disease that strikes down the "young and healthy", or the affliction hidden behind such thoughtless and abominable phrases as "it was their time" or "natural causes", the former will tend to attract more funding.

4) In a word, spirituality, whether spoken of or otherwise.

5) Too many crackpots through history have tried to peddle life extension, creating guilt by association.

2) regulation strongly constrains funding by steering it towards drug discovery.

3) people don't like being told they're doing it wrong, even when it is absolutely true.

4) the real goal of most researchers is to catalog metabolism, not to produce any way of treating aging.