Why? Because they are two different systems. That 37 year old active duty retiree actually completed 20+ years of continuous active service prior to claiming his/her pension. Most NG/Reserve guys haven't come close to 20 years TIS by the age of 37. NG/Reserves, in most cases, have a job/career in addition to thier military commitment....Active Duty guys don't and have to start over again at the bottom of the ladder when they get out. That military retirement helps close the income gap. "Because the Guard has to wait until 62" isn't a reason to put an age cap on AD.
You really hit the nail on the head.