Even though a logistics company uses trucks it does not mean they could build and operate a fleet of trucks.
You presume architecture firms would have any sort of capability to operate in software development. You might as well say they should create their own ink and papers. Software engineering companies are savvy in software.
Other companies aren't, and it is not expected that they would have any competence beyond their core offering.
Larger architectural firms like Zaha Hadid and Foster and Partners have developers in-house who work on internal tools for designers. Though I don’t know how many firms there are like this. Though I think architects in general have been lazy when it comes to tooling. The CGI industry has been far more involved in tools and open standards.
You presume architecture firms would have any sort of capability to operate in software development. You might as well say they should create their own ink and papers. Software engineering companies are savvy in software.
Other companies aren't, and it is not expected that they would have any competence beyond their core offering.