There are scanners out there for that purpose. Anything we posted which was literally "Check for this as we have seen x" would also be an advertisement to those writing malicious code "Avoid x as we are seeing it". This is, for example, the reason we don't disclose rules relating to our spam system. Any disclosure would result in telling spammers how to avoid it.
This said, however. It's simply not our responsibility to check the code of 3rd party developers. As with any developer you purchase any written code on the internet, you are purchasing on some level of trust and reputation.
This actually used to be the case. What's known as a loss leader. However, there comes a point where the benefits are not outweighing the costs. This is the case here. In the case of Apple and google, you are looking at marketplaces/stores of several million items, all of which make money for those companies. They also have very very very very large budgets for these things.
In our case, as already explained, the market for this has been in decline for quite a few years now. This is not to say there isn't a place for 3rd party items. However, it is to say that its not cost-effective, or an effective use of time, to host these items ourselves. Whether it be the files themselves or directories of files, these involve time from the staff here that are better put toward the main product for the benefit of all.
We will decide more on this nearer the time.