Because monetisation is logarithmic, while growth is supposed to be exponential for a while. You can go from $1 / user to $1.40 / user or $1.60 / user, but you

Because monetisation is logarithmic, while growth is supposed to be exponential for a while. You can go from $1 / user to $1.40 / user or $1.60 / user, but you can't go to $3 / user or $10 / user without some fundamental shifts that'll lose you users. You CAN go from 100 million users to 300 million to 1 billion.