Making friends mostly at work causes a lot of consensus bias related to economics because it means less exposure to people who didn't get as lucky with any part of the process of getting that job
I think it's fine to have your own biases, because you're human, and also to be aware that you do, so when you encounter people who are completely out of your normal sphere you will listen to them. It's folly to pretend to be free of imperfections (or even aspire to that). Nobody's above human nature, and there's no reason we should be.
I have acquaintances at work.
I always wanted a job that was like sitcoms based around work, where everybody is friends and hangs out. One time a building contractor moved in across the street and had his crew there for a while remodeling the house. I noticed four or five guys sitting at a picnic table in the front yard with beers, and I thought wow, so cool that the crew socializes on the jobsite after work!
It turned out not to be exactly like that - the two women in the rental next to my house were shooting porn in their garage with the door open, and the line of sight was from directly across the street where the guys had their table.
You’re a monster
Making friends mostly at work anywhere causes issues of selection bias, but it doesn't matter if it's work, school, church, your local pub, whatever. Balance in most things, as usual.
Throughout all my jobs, I've been always systematic in not creating any friendship or relationship. That's because I feel like workplace problems could affect the relation, or vice-versa, when personal disagreements could affect the workplace, because the humans involved would the same, me and my coworker. Imagine dating a coworker and then, eventually, falling into some disagreement (every relationship has one), then one of you (you or them) decides it's better to temporarily go apart so to settle things, but you both will need to see each one face to face tomorrow. You'll look in their eyes and you'll find a hard time distinguishing between your love and your coworker, because they're the same person (you still love them). There's also the presence of falsehood within workplaces, people that seems nice until they're at your back conspiring against you, trying to push you to the cliff. I faced lots of falsehood throughout my jobs. Careers sometimes involve competing against others and there are lots of people that takes this competition spirit too far, diminishing your job and your life for them to get some advantage (i.e. a better position within the company, a better wage, or even "for sadistic fun" of seeing others to be fired).
Maybe I'm wrong, but that's how I ever felt about workplace relations, I always tried to keep the workplace restricted to my professional persona. I'll be kind and helpful, but I'll kinda "robotic" to my coworkers and bosses. You could correctly guess that this led me to being a solitary person, something I actually always was, because I'm the typical former nerd colleague back at the high school, the shy, social awkward kind, never had real true friends, and love seems like some extraterrestrial fictional thing to me (not that I'm not capable of feeling love for someone because I once felt, but externalizing it and turning it into a relationship only happened in dreams, I guess).
So, in my opinion, it's not a trustworthy thing to make friends at work, especially if it involves possibilities of higher positions and/or higher wages, or a narcissistic boss that wants to be worshiped. But, as I said, maybe I'm wrong.
Plus, people quit and get fired, all the time.
In one sense, there's no point in getting attached to them, because they, like you and me and all of us, are expendable cogs in a capitalist machine.
On the other hand, those networks of "work friends" do tend to get each other jobs when they quit or get fired, so there's some value in making those connections if you plan to stay in the business.
I get what you're saying but I made friends with my coworkers specifically because they were able to acknowledge how lucky we got