Why do we need to have processes with operating systems?

as one of the oldest abstractions provided by operating systems, processes support the ability to have (pseudo) concurrent operation even when there is only one CPU available

because from CPU prospective disk requests take eternity, so a process is necessary to encapsulate any system calls related to information on the disk

processes are really not needed, future operating systems will do everything with threads only

because without process abstraction, modern operating systems cannot exist