SEL1 and SEL2 are about 0.01 AU away, 10 seconds light travel time back and forth, 4 times Lunar distance, 45 times the distance to GEO. From those two regions combined, all surface on Earth and the Moon and all of cislunar space are always in line of sight.
SEL1&2 are already used for scientific applications. But wouldn't they be useful also for commercial and military "inward looking" applications? Isn't it great real estate for communication and surveillance of military spacecrafts and of debris and impacting asteroids? Or are they too far away?