Years ago, you could probably leave the services after 22 years, and buy a house with your "lump sum". You could ride the rollercoaster of moves, knowing that when that 22 year point came, you could buy "back home".
However now, it isn't that way. The pension hasn't increased with the rate of housing, and now its "key" that you put roots down at the first opportunity. Getting a mortgage at aged 45, with a £40k lump sum, working for £30k a year, with a £14k a year pension isn't going to set you up well, when the average house is now £200k+. Good luck with that 20-25 year £160k+ mortgage!
The services promote housing, FHTB and all that Jazz, so when promotion offers a "move", a move away and "Living in the mess/block", becoming a "weekend warrior", then everyone has the right to turn promotion down.
Promotion and a move, living in the block/mess, getting GYH(M) is all a negative ~ stay in rank, in role and be happy... its just not worth the hassle. Let those who are single, divorced or child-less, dance to the tune of the promotion lottery.