In answer to the first: Because the information is unreliable without
more invasive technologies ensuring that the local file is up to date. To the second: Perhaps not, but if the information on bad actors (app distributors in this instance) you'll continue running a compromised app.
Are you familiar with OCSP conceptually? I have done a reasonable amount of work with signatures and certificates, including OCSP. All my experience is in a commercial, enterprise context but I think these technologies need to start filtering down to the consumer before the capability for security evaporates.
I think it's a consumer-positive direction for Apple to provide this service. I would be interested to hear from someone who holds the view that this is not a service, or disagrees in other ways, but I think this is the right direction for consumers. The alternative, as I see it, is that every person installing an app needs to start searching for CVE notices and headlines in trade papers declaring a compromise.
Apple have applied an enterprise middleware to their infrastructure. I think perhaps they could have been more transparent in the delivery. A lot of the outrage now is driven by people only finding out about the underlying process for the first time. I stand by the right of these companies to choose their business model to disallow (or restrict) execution of apps they believe to be compromised. I also firmly believe in a varied and free market for software, hardware, and infrastructure.
In essence: You can choose to use Apple and do it the Apple way. Equally you can choose to build your computer from components sourced from anywhere, install any free OS, and any apps. Personally I do choose to do it the Apple way, and I am inconvenienced by that from time to time. I curse my computer and its creators on a daily basis. It's part of the relationship we all build with our tools.
got a bit off track towards the end...