Repetition in architecture goes way back. Like way back. To the actual birth of architecture. The Greeks, Romans, Egyptians, Babylonians, Chinese, Japanese all found beauty in repetition and proportion. Every piece of architecture in Japan is laid out according to the 6' x 3' tatami mat. The rooms, the apartments, the rock gardens, the office buildings, even the real estate plots. The Greeks and Romans both repeated the 3 classic orders of columns in their temples. Egypt's pyramids are basically all the exact same dimensions, scaled up or down, and repeated.
One thing to keep in mind is that the construction materials can dictate how repetitive a building's layout and facade is. The Greeks built their temples out of stone (they were actually wood first, but stone later on, once the art was perfected) and stone can only span so far. In order to hold up the roof of the Parthenon, you have to place a column every 5 meters or so. Mies van der Rohe's favorite building material, steel, was still a fairly new type of construction material when he was designing. Steel beams and girders only come in certain sizes, and you can only set them so far apart as dictated by the construction codes and material safety requirements.
A repetitive building facade offers a sort of cadence to city life. It can provide a rhythm to the street. Also keep in mind that building facades in a city work together to provide a backdrop for the life and activity on the street, and a somewhat homogenous, repetitive fabric blends well into the background. We would all have ADHD if every building on the block was a Frank Gehry-esque titanium jumble. Every single building cannot be the star; you have to have a strong supporting cast (lots of "normal" buildings) in order the let that star shine.
Now, I will say that more than a few (okay, thousands) pieces of architecture are repetitive and boring simply because it's easier to design one section and then repeat it. Repeat it to death. But repetition in architecture was borne of beauty, not laziness.