Not at all the case. Architecture firms live and die by ADA guidelines. Those are hefty lawsuits if you design something not compliant. Fines can be in the millions. If there's nowhere to sit it's because the client, in this case the stakeholders on this project mandated it. Architects don't get to decide stuff like that.

Yeah no. Architect here. ADA compliance is taken incredibly seriously. Oh, and it’s also the law. And it’s also a decent amount of what you get tested on for licensure. Seating availability though is not ADA regulated.

As NCreature mentioned, the lack of benches probably resulted from a conversation like this:

Architect: “we’re proposing seating along the main concourse” Client: “is it required? Is it ADA?” Architect: “No. Legally it’s not required and it’s not an ADA requirement, but as a major public space—“ Client: “Yeah no. Homeless people could sleep on them and scare away shoppers and ruin our image. We need those benches gone.”

Lol making sure the building meets ADA and life safety requirements is like 30% of a contemporary architect's job. I'm only kinda joking.....

The ADA details are often the first sheet on the drawing set after the title page, followed by egress path diagrams.