Although there is an icon on the map it only shows the approximate location of said symbol in the game world. And once you find the symbol some of the Lost Sector entrances are rather well hidden and not blatantly obvious and require exploration of the vicinity to locate. The video makes that process much faster. It's not that it's terribly hard, but it takes time.
In addition, some people value intel on the enemy, approximate number, etc so they can be best prepared.
English
-
All of the lost sectors have been super easy for me to find. You just have to think about where you would put the entrance and -voila-
-
I've done every lost sector on every planet and didn't have a problem but that doesn't mean there's no one who wouldn't benefit from the video. That said, the longest I had to search for the entrance was about the same length of time I would've spent watching the related video. But the video shows more than just the location of the entrance.