There are few non-stops from SFO to Europe. Some may only be seasonal and not loaded in the system yet (Alitalia does a flight to Rome). You need to search each segment to see which is preventing the booking. It's sometimes one segment preventing the lower miles booking.

Do you have any status with Delta? If so, you can book the new economy comfort (more leg room, more recline) either free or at a discount depending on your level of status. Not as comfy as biz, but better than regular coach.

I always use itasoftware to search flight options. You can search one way from SFO to various cities in Europe and select non-stop. Then you can see if there are any non-stops easier as ita lets you enter multi cities in the search function. You need to use the airport codes and a comma (cdg,ams,bru). I wouldn't search to many cities at once as I don't think the search function handles a lot entered at once. I would only try the largest airports. Be sure to select non-stop under stops.
http://matrix.itasoftware.com/