I’ve posted a variant of this answer on other threads about Homebrew, but to summarize:

1. Homebrew is entirely maintained by open source contributors. Keeping thousands of packages up to date is a significant task even before considering maintaining the packaging core itself, and analytics serve as both a warning system and hard data for package importance, instability, etc.

2. Homebrew is somewhat unique among package managers because of its relationship with the host OS: it has no say over how macOS behaves, and needs to adapt quickly to changes made unilaterally by Apple. Analytics help detect that kind of top-down breakage.

FD: Current member of Homebrew, former maintainer.