Do we really need to upload Arduino bootloader for new Atmega IC
No, you do not need the bootloader for your chip to function.  The bootloader is merely a convenience.

If you are programming through USBasp you don't even need it on a "normal" Arduino board. 

All it does is allow you to program through the UART interface (or USB interface in the case of ATMega32U4 boards). If you don't want to do that then you don't need the bootloader.

If you do not provide a UART interface to the user that can be connected to then the bootloader would be pointless anyway since you cannot communicate with it.