Obviously you didn't watch the game and saw certain sections seating's being rather sparse in the background especially in the upper decks.
Notice the empty seats in the background? This shot was taken in the 3rd quarter.
It looks like it was during a break of some sort. Look at all the non-players walking around on the field, including a guy carrying a camera. That certainly isn't a picture of the stands during play, which would be the best indication.
There certainly have been a number of pictures of partially full stadiums, particularly for the 49ers and Rams. It's hard to know what ticket sales are actually like, since there are contradictory numbers floating around.
I know beyond a doubt Niner games are always half empty.I visit a 49er message board sometimes and even they have posted pics there of the same angry about how the fans need to get out and support them.lol
The Rams game however was the exception.It was actually packed.I like others here also assumed the stands were half empty as well for that game since they always are
However there was this one poster in another section that posted a pic to clarify it to this other poster he was incorrect saying the seats were half empty for that game. the pic he showed proved they were all full. I wish i could remember what thread it was where i saw that pic at.darn.
I am guessing the ONLY reason THAT game was packed is because SF fans same as me have been wanting the Rams back in LA forever now as well so many of the fans in SF who dont go to games anymore with them out of the city,did take the time this time to go see that classic rivalry.
NORMALLY that stadium always DOES look like that.

But they get excited about the Rams no matter how bad both teams are because of the history with each other so that game is always the exception.
Other than Ram games,that place is always half empty all the time.
the NFL has turned off many NFL fans because they are now seeing what I have the last 20 years that it is the NO FAN LOYALTY LEAGUE. the owners were so stupid with relocating all these teams they ignored the economists that it would bite them at the gates as it is now.
people who think the niners winning that people will then all of a sudden show up are nuts and dont know any better. Because In SF they always packed them in when they were horrible and the joke of the league.
Same with the chargers in SD. the NFL leaving LA has drastically hurt because other then diehards,the new generation did not have a team to root for so they found other things to do the last 20 years the fact there is so much to do in LA and the NFL is finding out it is going to take a long time to get the fans back because they are having to rebuild all over again to the NEWER generation of football fans who found a different team to root for,they arent going to all of a sudden stop rooting for that team they adopted
they were never embraced in st louis other than the greatest show on turf years and now they are back where they started when they got to st louis with half empty stadiums having to try and get a new generation of fans who adopted another team back to games again.
the NFL has royally fucked things up the last 30 years with all these moronic relocations and now it has esculated worse than ever with these recent asinine relocations of the niners to santa clara the chargers to LA.

the owners have KILLED this game.