Sending a chat message is a really low bar: people send off chat messages at will, without respect to whether someone looks like they're concentrating, wearing headphones, have the door closed, are in the office, whatever. This is fine so long as chat is regarded as async, but in a culture where people feel compelled to get them in real time, chat becomes super interrupty, even compared to people coming by.

If people exercise good judgement on ignoring notifications, it's less rough, though the tooling is really poor for using chat for async tracking, organization, triaging, and replies, even compared to emails or tickets.

bingo - chat interruptions are more manageable than a literal drive-by