Because they are afraid. They don't really know what is true or not and are hedging their bets.

my wife's uncle just passed away (why am i saying passed away?--he died) at 101. he had all his marbles right up 100. we had few conversations about religion. but i know he was a believer. at no time when he started to decline precipitously did he express more faith. he never asked to speak to a minister so far as i know.

Instinct from religious upbringing

They are scared shitless.

The possibility of the mind's ability to reason well apparently diminishes for some people as they age and suffer from brain function impairment. Fear and ego annihilation probably enter into it. Many older people feel more insecure as their abilities deteriorate both physical and mental. Woody Allen expressed that uncertainty and fear when he said, " I'm not afraid of dying, I just don't want to be there when it happens."

The deathbed confession of a famous evangelist of my youth went the other way--: he claimed he never really knew whether God exists and that his whole career had been hypocritical. (Of course, the faithful claimed that he had already “lost his mind” when he said that.) Also I heard that Mother Teresa made a similar agnostic confession toward the close of her life. Can anyone confirm this?

"I was thinking about how people seem to read the Bible a whole lot more as they get older. Then it dawned on me. They're cramming for their final exam." George Carlin

To me this simply screams bat shit FEAR.

they get afraid because none of us know what is ahead silly but understandable we all have the illusion of control and to not know is scary like jumping in a dark hole not knowing where the bottom is or what its made of

because they're scared. we assume that our consciousness dies with our body and they don't know how to deal with that. it's not true, but we don't know any better.