OS X kill terminal processes

I'm confused with closing terminal applications in OS X. Why processes are not killed after closing terminal app? For example I call python interpreter then close it with ctrl+z and when I try to close terminal it asks me about ruing python processes. Sorry for Russian in the screenshot but you can see 2 python processes(I called it two times).

OS X terminal screenshot

It's very aoying especially when you are working with serial port using minicom for example. You have to kill process manually after each call. Is there a way to kill them automatically?