You're culling in Lightroom. Right now you're either shaking your head saying "Oh HECK no! I'd rather have explosive diarrhea than cull in Lightroom!" (sorry for the graphics but it's that serious).
Or you're looking around, cringing, saying "Uh... y'all aren't culling in Lightroom? Did I miss the memo?"
YES! YOU MISSED THE MEMO! Culling in Lightroom is SLOW, you're loading images YOU DON'T NEED, and you're taking up precious SPACE (I won't even get into how friggin long it takes). QUIT CULLING IN LIGHTROOM!
If you have an Adobe Subscription, Adobe Bridge is free. There's also FastRaw Viewer ($15) that I use. You'll open the system, cull by flagging or starring from the SD or CF card, drag those images to your external hard drive, THEN upload those to your LR Catalog! This way you're not saving unnecessary files or bogging down your system by trying to filter through them! These systems are DESIGNED for culling! Lightroom... is definitely not.