If you spend time learning about how HR functions, it'll help you understand how things like promotions work. Spend time with marketing, and you'll learn lessons about human interaction (what gets someone's attention, how to write copy in a way that people understand, etc.). Spend time with sales, and you'll learn about relationship building. None of those things are unique to tech.
I'd even go beyond work-related stuff and say this attitude is universally positive. Spend time with contractors, and you'll learn stuff that'll help when you own a house. Spend time with teachers, and you'll learn things that'll help with raising kids. Spend time with doctors, and you'll learn what minor-seeming medical issues are worth taking to the doc and what might seem bad but doesn't warrant a doctor trip.
I'm probably biased because I'm a PM at an early-stage startup, which requires a very generalist skillset, and I love to learn stuff about other people's jobs.