The other thing the Windows ecosystem has that makes it more hospital for executable file viruses is a culture of user-to-user sharing of binary executables. I

The other thing the Windows ecosystem has that makes it more hospital for executable file viruses is a culture of user-to-user sharing of binary executables. In the UNIX world, sharing source is the usual vector for copying programs user-to-user. This was particularly true back when executable file viruses were at their most prolific - back in those days, if you copied a game from your friend at high school, that binary was quite likely to be several tens of generations removed from the original source. Each generation was an opportunity for a virus to climb aboard. With internet distribution of illicit wares, you're much closer to the original source.