In some cases, the failure is simple: they do not actually scan the application code. AV-Comparatives have found that they use only white lists or black lists, and sometimes very wide. They can resolve all applications whose package files start with "com.instagram", but it would be trivial to create unfair apps that use a variant of that name.
Attachments across the shoulder come from familiar security brands, with big names such as AVG, Kaspersky, McAfee and Symantec capturing everything. Those who did not, however, had a familiar pattern. Many are written by amateurs, cutting-edge cookie applications, or by companies that are obviously not focused on security. Anti-malware programs of 32 vendors in the test have disappeared in the two months since the test was conducted in January. However, this illustrates the challenge faced by Google and other app store operators. They can check if the apps are harmful to users or violate the law, but they can not impose the basic level of quality needed to maintain the safety of your phone.