Depends what you're doing with it. You can just glue this dev board in to your hobby system, or if you're making an interactive kiosk, maybe you want a usb webcam & hdmi screen. If you want to debug, those ports can be pretty handy, you can have a monitor and keyboard on it. If you do your own pcb integration, you can decide what ports you want on your board.
If you want to connect a screen, keyboard and mouse? Or plug in a wifi dongle? Absolutely!
And by the point you don't need them, you can graduate from the dev kit and spin your own PCB without them on, if you like.
The development kit will probably break out other signals too - but if you know what SPI and CSI are, you probably don't need to be told what an embedded dev kit is :)
Some people have different views on what’s an embedded system, but hardware serial, USB and Ethernet are tablestakes for interfacing with any most industrial hardware or for robotics uses.
