Why do some West African countries adopt the Unitary system of government while others do not?

Some West African
countries adopt the Unitary System of government while others do not for some of the
reasons below. 

• Population: A country with very small
  population may find it very convenient to
  operate the Unitary system rather than Federal
  system. Examples include Gambia and Ghana. 
• Flexible Constitution: A state or country
  that is relatively new may wish to adopt Unitary System because the Unitary
  Constitution is generally flexible  and
  easy to amend to meet changing situations.
• Insufficiency of  Natural Resources: If a country does
  not have enough natural resources, a unitary system of government would be
  preferred. 
•  Size of the Country: The Unitary system is suitable for a
  country which is small in size. It allows
  for uniform administration.
•  Homogenous population: If the people of a country have the same
  culture, language etc, the Unitary system
  rather than the Federal system of government
  would be preferred.
•  Absence of Minority Groups: Unitary system
  will work well where there are no minority groups..
•  Lack of fear of domination: In a country where
  the different sections of the nation do not fear any form of domination, the
  unitary system could easily be adopted.

In addition to the
above, some countries may want to adopt the unitary system because of its numerous advantages and features such as: 

• Cheaper to Run: The
  system reduces cost of administration 
• Speedy Decision
  Making
•  Uniform Development
•  Promotion of
  National Unity: Since the people are loyal to one government,
  National unity can easily be achieved
•  Absence of conflict;
  between ihe central government and component
  units