And you need to still do quite a lot of leg work getting users to opt in. With the recent death of the Reddit API my favored client is being adapted to Lemmy - but the news of that happening only reached me because I was following the news on their subreddit before the shutoff. Pre-registration feels like a huge waste unless your users are literally chomping at the bit.

Users install a whole bunch of apps on their phone when looking for a solution to a problem and a fair few of those are never actually launched.