Its backwards when you read it and redundant.

    def do_on_click(): # What's being clicked? 
        foo()
        bar()

    backup_system_panel.reset_button.bind(on_click=do_on_click())

Oh it's the backup system, maybe I should have named it that. Now I have to worry about reading backwards or keeping names in sync. Having to give it a descriptive name is like uneccessary comments. Giving it a temp name is ok but then you are reading bottom to top to know what is going on like you are programming in reverse polish notation or something. It can be multiple lines and scrolled off the screen before you know the context it is used in, instead of just being able to read top to bottom and get everything. Most other languages let you just stick it in line where it is used. It's error prone like C variables when they had to be declared up top.

Sometimes in other contexts it does make sense to do, but with other languages you can choose to pre-declare and name it or not. In python often you see code with all the error handling lambdas up top before you even know what is going on, when exceptions aren't a good fit.