I'd agree – there are real advantages in maintaining a friends group outside of work: you spend far less time griping about your day to day, and the connections you make are far more stable.

Get a beer once a month with coworkers, sure, but relying on work to be a primary social outlet always seems risky.

Yep, it’s more meaningful for someone to go out of their way to meet up with you (when there’s only friendship to gain). Also prevents mixing personal life with work.

My first job out of school, moved to a new city. For three year my only friends were coworkers. We socialized (drank) couple times a week and almost every damn conversation was work related, mostly complaining. I left that place because I "hated" it so much. I wonder how much those conversations contributed to it.