We don't. But dev teams keep creating them. It's IMO much more appropriate for new coins to make an announcement, provide a whitepaper + source, and start the

We don't. But dev teams keep creating them. It's IMO much more appropriate for new coins to make an announcement, provide a whitepaper + source, and start the network at time X. But I can (somewhat) sympathize with their desire to be rewarded. What if someone just aims their ASICs/GPUs/cloud cycles at their new coin for the first months after the announcement and reaps the lion's share of the rewards? While that seems unfair to them, it is traditionally the fairest/most honest method.