Because your in the Army, and under 30, and as such, your deemed not to be trusted ! I asked the same question when I was serving, and never really got an answer. If theyd given it me, I'd still be in. Excellent way for retention, giving money for house purchases, but, as I have said in other threads, the Army is slow on the uptake as to what is good for the moral and retention of its personnel.
You could always transfer, and enjoy a life on the open waves. Yoo-hoo-ho and a bottle of whatever, etc.
Count yourself lucky! The system was only introduced to the Army in 1996, up until then, there was nothing!!! The deal is £8.5K that can be used for any purpose associated with house purchase. This includes stamp duty, survey fees, solicitors fees, deposit (yes, part or all can be used for a deposit!). It can not be used for improvements prior to moving in or new furniture and the like. Payable over a maximum term of 10 years interest free works out to be about £70 per month. You can increase that amount if you wish but not really worth it on an interest free loan. It does affect your income tax as well until you have less than £5K owing. If you leave before the 10 years is up, they just take it from your gratuity. You can keep the deal if you sell up and buy again but not get a new one. If you sell up and move into quarters for example, you have to repay the balance. Once you have not been a homeowner for three months (I think) you can start the whole process all over again. If you elect to move into quarters and rent out your house, you have to pay the interest for that period only. I recall thet the rules are over 35 years old and have 12 years service. The scheme is managed by the Royal Navy and is, I believe aimed at their lower limits because of their situation whereby being at sea makes it difficult to house hunt and, they are generally more stable when on shore in that they do not move around as much.
I am not the expert but was one of the first in the Army to use this scheme and as such had to go through an application procedure that was akin to the Spanish Inquisition. Hope this answers some of your questions if not gives the solutions.
The system does need changing, people across society as a whole are buying houses at far younger ages than they did 20 years ago. If the minimum age is indeed 35 then it needs to lowered. 25 with 5 - 7 years service seems sensible. The existing limit seems to cater for those who are approaching their 22 and need to ensure that they and their family have somewhere to live following discharge.
I think the reason for a higher % of Navy personnel being home owners is acounted for by the majority of them spending much of their carreers either based at or on ships that operate from Portsmouth, Devonport or Faslane. For that reason they don't have to move every 2-3 years and are able to settle down and buy homes at an earlier age. The Navy have quite sensibly decided to give their bloke a helping hand.
Why can't the Army change with the time and follow the Naval example? Probably because the hierachy still view us as something off Lad's Army to be treated like children if below a certain age, or rank (usually Sgt). It would definately help to aid retention if th Naval system did go purple.
Long Service Advance of Pay is available to all regular personnel aged 35 yrs or over in the Army and RAF, and 23 or over in the RN, who are serving on pensionable engagements. Advance is upto a max of £8500 remembering that loans over £5000 are taxable.
There is no logic for this age difference. PS at Upavon are trying to redress the difference between the RN and the Army/RAF age requirements with the treasury, ideally to make it available to everyone aged 23 yrs or over.