Why does Norton miss so much?

I have Norton Anti-Virus, I pay for the  subscription, It is always updated, runs its scans and yet, I have to use other free anti-virus software to clean up what norton misses?  It seems to be alot.  What am I actually paying for?    Its like hiring a wedding photographer that only takes selfies.   Why did it miss these:

 

Registry Key: 1
PUP.Optional.APNToolBar.Gen, HKU\S-1-5-18\SOFTWARE\AskPartnerNetwork, Quarantined, [10872], [186876],1.0.951

Registry Value: 1
Trojan.Fileless.MTGen, HKU\S-1-5-21-2442580863-770913025-2777333265-1000\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\RUN|^GAGHILX, Quarantined, [452], [262349],1.0.951