For most small businesses like mine these chats go straight to the phones of the founders. You've got a direct line to the most knowledgeable person about the service.
So to your question, many people use them successfully.
This literally describes 90% of successful marketing tactics.
We, software devs, can be unnecessarily pedantic and nitpicking.
On the short term, yes. But as soon as I'm not required to use Slack anymore, I will remove it from my Mac and advise anyone against it.
So on the long term, I'd say a business would be better off not making the balance so precarious.
In this case, it's making the internet a less productive place to be. So many chat widgets I encounter are now used for growth marketing, not actual support, that whenever I see one I expect it to pop up and seize my attention at an inconvenient moment. Now that everyone is doing it, it's ruining it for everyone else, and something like this browser extension shows up.
If it works for you, then great, I suppose? But if I were the internet dictator I would have placed a ban on preemptive chat messages in these widgets years ago.
Chat widgets can be a good thing but its all about how you use them within the company... I'd say, definitely no popup, when nobody is available, just don't show the widget and redirect to a contact us form or email address. Make the support flow as dynamic as possible.