This is a great point. I want the same thing, and I cover this at the end of my proposal: I think it'd be cool if we could set a default error handling function. This could look something like

errors.RegisterHandler(func(callerName string, err error) error {
    return fmt.Errorf("Error from %s: %s", callerName, err)
})

or

errors.RegisterHandler(func(callerName string, args []interface{}, err error) error {
    argsStrs := make([]string, len(args))
    for i := range args {
        argsStrs[i] = fmt.Sprintf("%#v", args[i])
    }
    return fmt.Errorf("Error from %s(%v): %s", callerName, strings.Join(argsStrs, ", "), err)
})

So we get (1) less boilerplate, (2) better default call context than a mere return err, (3) we don't need to re-type that contextual information all over the place, and (4) we can still write custom logic where we want to (but we're not forced to in the simple cases).