Nintendo is a company that cultivates a child-friendly image, going as far as asking players not to spend too much money on microtransactions in their games. Then they added a subscription fee on top of microtransactions and loot boxes in Mario Kart Tour.
Once upon a March 2019, Nintendo asked players not to spend too much money on their smartphone titles, aware of the microtransaction potential on iOS and Android platforms.
Furthermore, CyberAgent Inc. , the developers of Dragalia Lost who worked with Nintendo on the project stated that the company was not interested in "making a large amount of revenue from a single smartphone game" which testified to to prevent spending too much on smartphones.
Fast forward half a year and Mario Kart Tour has been released with no multiplayer modes. The game does, however, have a $4.99 that is slapped on top of the existing microtransaction options. One funny note is that this is a subscription for a single game and is more expensive than Nintendo Switch Online Pass ($3.99). The 200cc mode was also locked behind the subscription at the time of writing.
The game also features loot boxes and regular microtransactions. Rubies are the in-game currency that can be purchased in various packs, from the $1.99 for three Rubies to $69.99 for 135 Rubies.
To be fair, Rubies can be earned in-game but it doesn't change the fact that it is still a paid currency. On top of that, Rubies can be used for the Pipe which is the loot box mechanic of the game, giving players a chance to win new drivers, carts and gliders, as seen in the trailer below.
Android and iOS devices are not first-party hardware for Nintendo and it's hard to gauge how much child control they will manage to implement in Mario Kart Tour, if any at all. One thing that is certain, however, is that this monetisation model tells a story that is in contradiction with the statement that Nintendo doesn't want that much mobile revenue.