They're common in vending machines, libraries, ticket machines for bus/train, etc. as change because they're easier to distribute than single dollar bills by a machine
You're fine - I grew up in a rural state, and I thought they were super rare until I lived in a city where the public transit system gave them as change.
Nope, I haven't seen one since the early 2000s, when they rolled out Sacajawea dollars and then stopped a few years later because boomers were afraid they'd confuse them with quarters.