Civil service is an option for those who cannot fulfill their
military service in those countries where the army is based on general
conscription. At least in Finland - I suppose this applies to all countries - you have to have
moral motivation choosing civil service instead.
An exaggarated view of militarists is that civil service is just way to avoid hard and patriotic duty of national service in the army. Civil service is an option for lazy glue-heads who are likely to be homosexual. On the other hand, conscientious objectors think that civil service is just a punishment for morally superior people.
Civil service takes 395 days in Finland whereas the shortest possible military service period lasts only 180 days. Human Rights Agreement says that civil service shouldn't be more than twice as long as military service. Civil service should be carried out working for non-profiting organization, say state, commune or NGO.