It's not just the pre-mine, it's about the emission schedule. Take Monero or Dogecoin for example, both have a very steep emission curves, with the vast mayority of the coins mined on the first months/years after launch, disproportionately favouring early adopters. It's not technically a premine but has the same results in practice, that can be considered scammy. Grin has a linear emission schedule, which disincentives speculation and promotes a fairer distribution, with inflation tending towards zero. Bitcoin sits at a middle ground: its halving schedule favors early adopters but not as much as Monero/Doge.
It's a good point -- all of these things (pre-mine, emission, the resultant distribution, the identity of who the coins have been distributed to) are all elements in how monetization and price discovery unfold.
That said, I'm less certain than you seem to be that the 'right' answer is known. The exponentially decaying distribution of btc may have been the key to its success, creating stakeholders who had a giant vested interest in building it out and getting it accepted. (I'm not sure if this is true, but it's not an idea you can dismiss out of hand, imo.)
The success of Grin -- or lack of it, from a price standpoint, vs Monero for instance -- might be evidence of that, too, although there's a lot more in play, obviously. I also think Monero's tail emission strategy is sound. I expect that btc will wind up doing the same thing in a decade, though it is heresy to suggest it. We'll probably know the answer in less time than that.
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