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Most of that stuff was there because the Auschwitz extermination camp was just a small part of a larger network of camps and factories around the town of Auschwitz owned by enterprises such as Siemens and I.G. Farben.
The small hamlet turned into a modern German town with around 40k inhabitants at its peak. Mostly because it was an important railway junction and mines were located nearby.
Outside of what was known as the Auschwitz extermination camp they also had factories (Monowitz/Auschwitz III), housing and other facilities for workers, scientists etc. .
It was not at all uncommon that you find such facilities for the German workforce that ran the factories or the guards stationed there.
The various sites were compartmentalized however so it was not like the prisoners or slave laborers ever got use any of the facilities or the workers could see what was going on next door in the prison camps.
In fact inmates from Auschwitz had to built most of the factories as an incentive for corporations to open factories that could support the war effort.
It was all part of the SS grander scheme of turning undeveloped Soviet/Polish farmland and towns into German industry and agricultural sites using slave labor to construct them.
