See, having just been diagnosed with something that needs folks to help me out to stay well, I totally see the opposite happening. Everyone asks waht they can do and how they can help. So, I think most folks just forget or don't notice when they "slip up"; it's not on purpose.
I mean, in my area, my kids joined a new group this year that had an outdoor potluck 2 weeks ago. Since it was our 1st time, I let everyone know who I was, and that I needed anyone who had been sick lately to let me know or just meet me next time. To remind everyone, I wore my leukemia shirt. And at that event, which I admit I kept my mask on and didn't eat, b/c this was a potluck and it was WELL-attended, so I was keeping myself safer...well, folks did everything I'd asked for in email. Lots came up to talk to me, but gave me a bit of a bubble, no one was freaked by me keeping masked up, and no one minded I didn't eat (I did get a lot of questions about how I found out I was sick and stuff about the disease, but I'm sure I'll get that forever
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TL/DR -
with a vacation parade, I'd chalk it up to excitement and not intent - I'm sure if Disney through down some temporary chalk bubbles and told folks to stay in them, everyone would have...