Because the British hated the French and feared that the French would try and take over the British Colony
Between the 1870s and 1900, Africa faced European imperialist aggression, diplomatic pressures, military invasions, and eventual conquest and colonization. At the same time, African societies put up various forms of resistance against the attempt to colonize their countries and impose foreign domination. By the early twentieth century, however, much of Africa, except Ethiopia and Liberia, had been colonized by European powers.
The European imperialist push into Africa was motivated by three main factors, economic, political, and social. It developed in the nineteenth century following the collapse of the profitability of the slave trade, its abolition and suppression, as well as the expansion of the European capitalist Industrial Revolution. The imperatives of capitalist industrialization—including the demand for assured sources of raw materials, the search for guaranteed markets and profitable investment outlets—spurred the European scramble and the partition and eventual conquest of Africa. Thus the primary motivation for European intrusion was economic.
Civilians did things such as mend clothing for soldiers, make ammunition from household silver, and many women followed their husbands to the battlefield where they washed, mended, and cooked for troops. Very few were able to fight in combat, but some women did.
The single largest complaint by the colonies against their English rulers involved d) the form of self rule. The colonists were very against the oppression they felt due to the British ruling the colonies (as they ruled virtually all aspects of public and private life). They were also imposed harsh taxation measures and their economy was completely monopolized by the European superpower.