You really think there are millions of viruses for Windows, which still have an active entry system?
You really think only 10 viruses have been created for OSX, since day one?
Yes I really do. The world is full of unpatched systems and antiquated Windows versions so a large part of those viruses have an 'entry system'. We even had a customer who was using Win95 for business just a couple of years ago
One point of entry is the moment of install due to Microsoft not supplying patched and updated installation medias without buying a new license.
The amount of 'in the wild' active viruses for OSX is around ten afaik. Feel free to prove me wrong. Even if it was 100 in reality it completely disappears in comparison to Windows viruses and malware.