Sure, there can be cultural hurdles there, but those exist in the office as well. "Jane has headphones on, she's heads down and will be upset if I bother her now" "I want to ask Steve for help, but he rolls his eyes any time I approach him" "Sam said they'd give me a hand this afternoon, but I can't seem to find them anywhere in the building"

Agreed, but the things you’ve mentioned would all clumsily be grouped under the “busy” Slack status even though they mean quite different things.

And further, seniors should never be upset that a junior is coming to them for advice, mentoring less experienced people one of the main responsibilities that comes with seniority. (This isn’t to excuse help vampires of course.) So I disagree with with the framing.