Why 8051 microcontroller uses four different ports for I/O instead of using address bus and control signals
One is a processor the other is a microcontroller, two different problems being solved here, in order to do what you can do with the 8051 you need to use a lot  logic and an even bigger board to hold the extra chips (from that era, or at least one from this era), very very inefficient.
While configured as four ports from a labeling perspective and in some ways in logic, it can be used as many ports one to a few pins at a time.  And often mcus multiplex the pins to allow for different internal peripherals to be possibly used based on the application, even more logic and an even bigger board if you wanted to emulate that with an 8085.
Why cant my compact car haul a cord of wood like a pick up truck can?  Just because they have four wheels and a seat doesn't mean they all can do the same thing.  Just because they have processors inside and start with an 8 doesn't mean they can be used in the same way.  One is for one job, the other is for another, you can by adding more stuff on get one to kinda do the other (add a small trailer, and hope you dont burn out the transmission or engine).