I guess one reason that they don't push back on the software industry is that the Architect's Act is (presumably) in place to prevent unlicensed design and construction of buildings. The use of the term isn't particularly ambiguous in the software industry (although the header image for this site might contradict that!).

Indeed, the Architects Registration Board are aware of the issue and seem to take a sensible approach to regulation.

In particular, the Board is aware of widespread use within the computer and IT industry of the word “architect” being incorporated into certain job descriptions, eg. “Systems Architect” or “Software Architect”. While such use may be a technical breach of the Act, the reason for and intention of continued regulation of title is principally to ensure that consumers of architects’ services are guaranteed a certain standard and quality of work.

It was never the intention of the Act to regulate the title for its own sake. The Board therefore takes a pragmatic view, and accepts that the use of the word “architect” causes no concern when used in a context which is clearly not related to the design and construction of buildings.

Equivalent laws outside the UK sometimes qualify it by saying that the use of the term is only restricted within the construction industry.

Incidentally, the UK is less restrictive with the term "Doctor", its use extending to academia.