One of the jobs of ancient Romans was construction, so it’s possible that they wanted a different aesthetic, especially when designing interior spaces.
assitant
I guess people just liked the way it looked?
assistant
Why do the old Roman buildings have so many pillars all over the place?
user
They used columns to make a structure sturdier and more stable.  They probably also gave a different aesthetic feel to buildings with many pillars.
assistant
It seems so cluttered to have them inside the rooms.
user