900 Randolph is an actual highrise tower, and it's residential - there are valid reasons to use concrete. And they couldn't do an exposed steel frame if they wanted to, it would fail the energy code. In our climate, the building skin always has to be separate from the structural frame with an insulation layer between.
1020 Randolph is a little 5-story midrise, and it's office. The use of concrete is purely an aesthetic choice so they could do mushroom columns with drop caps and make it look like an old warehouse inside:
https://1020wrandolph.com/