iPhone started 4GB.
then 8GB
then 16GB.
It's been 16GB since 2010, they got stuck for some reason. Well, for one, it's been largely sufficient for the majority of their customer base.
It's not atypical for them to increase the base storage. They've done it twice before.
16gb seems to be the starting point with most manufacturers at the moment. 32gb will surely be the base one day. Maybe next year.