1. No one will ask 4 RCTs 4 parachute effects.
If you made a pill that 100% cured advanced Alzheimers, and you gave it to 10 severely demented people and they all were restored, we would use it immediately
Much of this low hanging fruit may be picked
And you are left in a world where there are 10^8 or 9 hypotheses per year, and most don't actually work;
So pretest prob = low
and at best your Rx is not a parachute
Which is why people keep asking for them for whatever malarial drug, vitamin, or arthritis medication has the most exciting in vitro activity of the day.
Well, we don't even have a cohort study to show you shouldn't put your hand in the garbage disposal and hit the on switch.
RCTs for interventions of putative benefit, with at best modest effect sizes aka most biomed