Carts are abandoned for reasons a chat can answer
Most abandonment happens at the moment a shopper meets an unanswered question. Shipping cost that only appears at checkout, a delivery date that might miss an occasion, uncertainty about whether a return is free, a size chart that does not say what it needs to. None of that is a payment problem. It is an information problem, and it happens while the visitor is still on the page.
That window is where a chat widget is useful and an email is not. The question gets answered from the same shipping page, returns policy and product data you already publish, in the visitor's own language, before they close the tab.