These unusal deaths, along with the flavour-text and title, should prompt us to look into the chances of these deaths. Googling some of these terms should yield a reference to micromorts, a (somewhat contrived and unlikely evidence-based) unit of measurement for chance-of-death-per-million. Simply now reference the micromorts for each of the gravestones, assuming that micromorts are additive in the case of multiple activities. Then, use the A1-Z26 code to yield the solution of LIFE INSURANCE.
Activity
Micromorts
Letter
Went for a swim
12
L
Went hang gliding after spending 1 hour in a coal mine
8+1 = 9
I
Got out of bed at 45 year old
6
F
Went scuba diving (trained)
5
E
Got out of bed at 45 year old then went rock climbing
6+3 = 9
I
Took MDMA after eating 1000 bananas
13+1000x0.1 = 14
N
Encountered 190 kangaroos
190x0.1 = 19
S
Flew 1000 miles then played American football
1+20 = 21
U
Got out of bed as an infant <1yo, then went rock climbing
15+3 = 18
R
Ate 100 char-broiled steaks
1
A
Underwent general anaesthetic for an emergency operation after living 8 months with a smoker
This puzzle also serves a great example for why Puzzle Hunts are so fun: there's just so much random interesting stuff out there that one uncovers in the process of solving and writing. I went on a bit of a micromorts rabbit hole, looking into the methodology behind it and whether it is actually any use as a tool in decision theory. I highly encourage you to do the same. And maybe even consider hanging this up on your bedroom wall.