I noticed that there is a lot of newcomers, who lose interest before they get a weekly reward. Instead, they would become loyal members if they'll get the motivation before they leave, IMHO. That is not only in my case, but that is a general picture accordingly to the simple math above.
There are already other benefits like rewards points, lottery tickets, and interest. If people aren't motivated to stay longer it's not because you're not sharing sats often enough with them. It's because it takes such a long time to reach the withdrawal minimum if you're just a faucet user.