In my experience working on large apps like Airbnb we try to get ahead of the problem even before approaching the cellular limit, since a smaller size helps acquire and keep users, and we want to avoid architecture decisions that would become a problem down the road.
It's not too rare for one of these low hanging fruit optimizations to be accidentally introduced in a large company, with testing on every PR you can catch them before they‘re introduced. Binary size is definitely what changes most often at these large companies and that's why our continuous monitoring lets developers know exactly the granular binary size affect of a PR. With a lot of code, things like exposing Swift functions to Obj-C which introduce new metadata can frequently be mistakenly added. For enterprise companies we also track the biggest modules in their binary, so eng managers can get a better understanding of where the size is coming from.