sorry, long post:
The way I always saw the IRR was this.
It had 3 main intents and a fourth un-intended:
Intended:
1) A place where people could finish out their 8-year MSO, if they didn't already do so in Active Duty, which most people don't, since they normally signed up for 2-6 Active Duty years. For this group, there is no need to get Qualifying Years and it is from this group that the Navy gets their main batch of people in case of WWIII because, just having gotten out of Active Duty, they are the most "fresh". The high mobilization "mis-fire" rates encountered from trying to mobilize SELRES individuals (not so "fresh") masked the utility of having the IRR as a backup force.
2) A place to take a break from SELRES (due to personal issues or no SELRES slots available). Here the intent was to just stay in the IRR 1-2 years to sort your stuff out and still be able to earn Qualifying Years if you desired (hence the Correspondence Courses, Funeral Duties, etc.).
3) A place to let those that got out (really pushed out) of Active Duty with more than, let's say, 12-16 years (think LCDRs and E-5s,+ etc that did not advance) and still provide a way/place to get something out of the time they have already invested in their careers/lives. This option could also apply to senior individuals that could not get SELRES billets due to unavailability but still wanted to reach the 20 year mark. Remember, before BRS it was 20 years or nothing (for both Active or Reserve). People in this category had one remaining option, depending on their own initiative and personal situations. The O-4 20 Year Commissioned guarantee and HYT of E-5s and above are good proof of this.
Unintended:
4) The problem of people going into the IRR to earn points was certainly exacerbated by a lot of the SELRES billets going "below the line" (IAP - In Assignment Processing) during the 2000's, which would flag the people filling those billets for mobilization. I remember a lot of people strategically opting to go IRR to minimize their chances of being mobilized.
Also, the number of Inactive Duty Points a person could earn went from 60 to 90 in 2003, then up to 130 in 2008. That's more than double.
Like subreservist said: "A member could literally do an active duty 2 year commitment, followed by 18 years in IRR and earn a retirement." And, if done in the last 15 years, a pretty good one at that if they maxed out. I am sure that there has always been, going back forever, people that took advantage of how the IRR system worked to get to 20 years.
But, recently I am sure the Navy saw a significant spike of this type of group and I am sure the Navy ran the numbers and did not like what it saw.
The new Blended Retirement System now allows a person to walk away with at least something if they get out before 20 years. The longer a person remains affiliated (Active Duty or SELRES), the more they can walk away with. It covers those that serve 2-16 years in Active Duty/SELRES.
The new IRR policy then covers those in the 16-20 years range (with Sanctuary covering officers in the 18-20 year mark).
And, finally, the new IRR policy finally allows a way to block Group #4.
It was good while it lasted . . . .