Also, it costs less oil to build than a bunker of the same age. Considering what these two structures represent, that makes no sense. One is a parking spot for your tank, the other is a complex system for guiding missiles.
Also, the timeframe is completely inaccurate historically, the first underground missile silo wasn't built until the 60s (https://en.wikipedia.org/wiki/Missile_launch_facility). And if you think about it, it makes sense, since it requires computers to operate. 1960 is Cold War Age, not Global. Global is WW1 (early 1900), Atomic is WW2 (1940), neither age is accurate for the silo. If silo was added to Cold War Age instead, with a proper counter-weapon (a mobile high-range missile launcher for the attacker), we wouldn't be having all these complaint threads. I hope Nexon is reading this.
Gotta correct you here. Global age is WW2, Industrial Age is WW1. Atomic is directly post WW2, 1945. - 1950s or so. Which makes Cold War age in the 1960s.
This wouldn't be the first time historical inaccuracy was commited in the game (Chevaliers in Iron Age).