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.

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.

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.

I have acquaintances at work.

I get what you're saying but I made friends with my coworkers specifically because they were able to acknowledge how lucky we got