xbecause the lost the tech during reaches glassing by the covenentTo expensive.Because we had many years of peace?Mainly because they ran out of time and money to train and manufacture them.
They said that a few spartans were as expensive as a group of spaceshipsran out of money plus all there facilities were destryedcoz they were overpowered lol
The reason they stopped making spartans is because they never started. Dr. Halsey was the only person smart enough to make spartan armors and that armor made them spartans. Thats why the only spartan alive today is good ol' John"Master Cheif"(Classified). The reason he survived is *spoiler* Emile and Noble 6 got master cheif in the sky while inside the piller of autumn. If they hadn't got the autumn to safety John would've never lived and the covenant wouldn't have anything in the way of world domination and wouldn't join the battle for survival with you.