I’ve signed up for waitlists and bought things from some of them, and I’ve launched products to waitlists I built (and made some sales on launch day).
I think a few things helped with that, but one difference that stands out is where the subscribers came from. Mine were mainly from Twitter or people already reading my blog, so they already knew who I was to some degree and had some reason to believe I could help them. It’s a much harder job to sell to random people who came from an ad, who start off with a lot less trust. Any missteps in the copy/problem you solve/etc are magnified because random people are just looking for any reason to hit the back button.
I was on the Analogue Pocket waiting list and also the Framework computer waiting list. Still on both actually, though I've had the chance to purchase it (well at least the Pocket) and have not yet.
I think a few things helped with that, but one difference that stands out is where the subscribers came from. Mine were mainly from Twitter or people already reading my blog, so they already knew who I was to some degree and had some reason to believe I could help them. It’s a much harder job to sell to random people who came from an ad, who start off with a lot less trust. Any missteps in the copy/problem you solve/etc are magnified because random people are just looking for any reason to hit the back button.