Can you not just smile, wave and keep going about your business?

I primarily do this when I run into co-workers when I am with family or vice versa. I'd rather not mix my personal and work universes, and when I am away from work, I really don't want to think about work.

This only bothers me if I've already said hello. If I'm out somewhere and recognize someone but neither of us say anything, I'm not offended because I also didn't say anything! Sometimes, like you said, you just don't have the bandwidth. I also sometimes can't place people right away -- maybe we worked together? Maybe grad school classmate? Maybe our kids were in an activity together? I've lived in the same place for two decades and have met hundreds (thousands) of people and talked to them a few times and then never thought of them again.

But if I see someone I know and take the time to make eye contact and say hello, it is incredibly rude when people don't say hello back. I'm sure most of the time it's just they don't recognize me, which is fine -- I've been there. But if someone says hello to you, the bare minimum you can do is say hi back. As a PP said "Hi, nice to see you," and then continue on your way, even if you can't place them. It spares them that feeling of being invisible, or feeling embarrassed. It's always really weird to me when people won't even go to this trouble.

Um yes I do this.

I went to high school in this area, so it's not unusual for me to run into someone I know from 20+ years ago. I just don't always feel like chatting! Or it's someone I kinda know, but not really, and I just don't want to do the whole "heeeey! how ARE you?!" bullshit. So I run. I try not to walk past them though....

No, I always say hi. It costs me nothing and may improve the other person’s day. Or it may ruin it, if they hated me. Win-win in my book.

My excuse these days is the mask. But really, sometimes I just do not recognize people in masks/with sunglasses on.

Some people have facial blindness, and they don't recognize people when they see them in a different setting.

I do this sometimes and masks offer an easy excuse. Part of it is that with some people there is this expectation you are going to stop and have a whole conversation, and sometimes I just can't do that. Maybe I'm on my way somewhere, but often it's just that I have limited time to be alone (I have young children, and... pandemic) and I don't always feel like talking to people.

We should really normalize just saying hello and moving on. Most of the time it's not like your long lost friend or something -- it's someone you used to work with, or a mom whose kid went to playgroup with yours. Someone you know and like but don't socialize with and don't really have a lot to say to. Usually people will ask after my DH and kids, which is nice, but you can also tell they are mostly being polite. And I'll do the same thing ("Oh how is your job going? I remember you started a new one last I saw you."), but I'm not super invested in the answer. I just want to go back to being alone.

I think we're all just kind of burned out right now and need to cut each other a break. You're okay, OP.

I've done it often and feel little guilt. Hell, a few years back, I saw a first cousin at Giant who I haven't spoken to (no hard feelings) in ages, and I pretended not to see her. Granted, I do feel somewhat troubled by that (lack of) interaction, but nevertheless, it's easier to pretend sometimes than to engage in awkward conversations and promises to keep in touch/do lunch, which you know you won't do.

My DH was in the grocery store and saw the pastor who married us, and he admitted to hiding behind a shelf until the pastor passed by, lol.

I don't have a good memory for faces or names (ADHD) and I'm sure I've walked by people I knew without recognizing them, if they were dressed differently, with their hair up instead of down, etc.

Because of this, when I'm sure I recognize someone, I always wave at a distance or say hello if I'm near them.

I don't pretend not to see them. I also don't stop for a conversation, though, if I'm in a hurry or just don't have the energy or bandwidth (or don't really like them). I just say, "Hi! How's it going?" and don't really stop. You can greet someone without engaging in a conversation beyond that.

You're

I used to do this, but then when working on social anxiety forced myself to at the very least look the person in the eyes, smile, and say "hello. I hope your doing well." 95% of the time I felt better after the interaction.

It depends. I have had people pretend not to see me, people who have been to my house for dinner multiple times but who I've not seen for maybe a few years, do this.

I have also done it once or twice - with an old co-worker who I never knew particularly well.

Sometimes it is better than an awkward conversation.

Anyone else do this when they just don’t have the bandwidth?

I glanced in an aisle at the store and saw an old coworker walking my way. I tried to act normal, feign ignorance and ignore, but I’m pretty sure we made eye contact. I just didn’t have it in me to make small talk, so I left the aisle. I feel like crap for doing this, but she didn’t exactly try to spark up a conversation either.

Do people actually engage in every acquaintance they see out in public?