In Britain, the system of recruit enlistment was voluntary. But not many citizens of the empire agreed to join the army and spend a decade and a half in army service.
A large part of the army consisted of foreign mercenaries. The British recruiters didn't have many options where to draw volunteers from - they would typically conscript from prisons, taverns, and similar institutions.
These people went in the army for varying reasons such as: boredom, being seduced by regular pay and food, a thirst for adventures, so as to escape the law, obligations or women. The majority of them were a little crazy, adventurers or just simply criminals.
Only strict discipline, based on the inevitability and cruelty of punishment ensured obedience. For these reasons, "the abyss" separating officers from common soldiers of the British army was much bigger than in the other European armies of that period.
Besides that, the majority of regiments were financed from personal pockets of noblemen who usually acted in the role of colonels and did not participate in the command of operations. The role of commander in a regiment usually lay on shoulders of the lieutenant colonel.
As history has shown, this kind of system was effective, as the British infantrymen were always well drilled and trained to shoot.