An who retired sold his commission, and for those without a significant private income the proceeds of the sale was often a crucial part of their retirement planning.
Officers who died, or were cashiered, could not sell their commissions, but the same rule applied to those who were promoted from the rank of Colonel, to that of General. I can't give you an example offhand, but apparently there were cases where Colonels were outraged to find themselves promoted to General because it deprived them of their colonelcy, the sale of which had been intended to finance their retirement.
Was there something similar for the British Navy?
I was somewhat aware of this practice, but not in this detail.
Quite common for the 2nd son in a landed family whose older brother was going to inherit the manor or whatever holding the family had, to have purchased for him a commission in the army.
Don’t know if it was good for the army, but better maybe for the 2nd son than drinking, whoring and gambling in London.