Why do the Russians keep making ICBMs?

Why do the Russians insist on creating new ICBMs so quickly when we (the United States) rely on the old Minuteman III missile that was subject to now carry only one warhead, and we even retired our MX missile. True we have the Trident II which still has MIRV capability and is an extremely accurate and far reaching weapon, but due to the pacts we've made with Russia, the MIRV storage was reduced to about 6-8 from I believe an original 12-16. I only see Russia getting rid of old systems that were becoming obsolete. Why don't they get rid of the new ones? Are they so paranoid to think that NATO will be able to create an anti ballistic missile shield that could render their missiles useless even when our own scientists say this is impossible with Russia's immense stockpile of warheads? WHY, please give a good reason that is in detail.