about answer " do not detected some threats "

Hi ,
i sent a .zip file included near 5500 threat sample files .
 
when i scan those files with webroot Secure Anywhere only detected near 500 threats and do not detected more than 4000 files .
 
then I scan these files with other AV same TM, ... and they detected near 5000 threats .
 
then i sent all 4000 sample files for webroot threat research .
 
after near 3 days again i check files , but agaian webroot do not detected their .
 
send a request to webroot support about why after 3 days again webroot do not detected these files ?
 
they answer my question :
 " "
Hello,
This appears to be a collection of very old threats that will not even execute on any of the Operating Systems that are supported by Webroot SecureAnywhere, which is why they are not being detected. We focus on current threats that are still being seen in the wild and have the potential to infect our users. If you have samples of any current infections that are being seen in the wild and currently infecting users that you believe we are missing, we would happily take a look at them.

Thanks,

Webroot Threat Research
" "
 
But i have a other question :
 
Why other Security Companies Specially most valid Security companies same SY and TM detected old threats ?
 
I think this questions and topic help users to more understand about Webroot AntiVirus Products Operation .
 
Thank you .

Amir