Why is it difficult to travel through africa?

Among other things:
1. Infrastructure issues - poor road and rail links.
2. Security issues - ongoing civil wars and ethnic and religious conflicts; poverty related crime; tense border areas; unsafe airlines and land transport
3. Governance issues - customs and immigration officers and local officials who are uncooperative about or unfamiliar with tourists' needs

because Africa has a large area which all Composed of Desert
and distance between cities is far
no railways lines connecting each country with others like in Europe
General poor case in money sources
and Lot of reasons