Part of Nintendo's long term strategy is to integrate the My Nintendo loyalty programme with multiple apps and even tie-in with visits to special locations and similar incentives. It's early days, however, and the Platinum points currently revolve around weekly logins to Miiverse, the eShop and My Nintendo itself, while small daily rewards are up for grabs in Miitomo.
Miitomo, for various reasons, has likely dropped off the radar for plenty of people, but Nintendo is offering a tiny bit of extra incentive to tempt you back. A new daily 'Mission' will reward you with 2 Platinum points every time you answer the app's 'Featured Question'. Crikey, break out the bunting!
Cynicism aside, the daily and weekly missions add up nicely in terms of points over time, so if you do happen to nip onto Miitomo this is a nice little extra.
So there you have, don't spend all those points at once.
With thanks to Doctor Overbuild for the heads up.