Why the boundaries of some countries are such direct?
Historically, the government is associated with the settlement of border lands. The boundaries carried out without any accounting of the national characteristics of the territory are called superimposed.
Borders of Africa, places in right corners

Such in our world a lot. For example, in Africa, where the section of the territories in the XIX century occurred behind the back of the local rulers and against the desire of ordinary people. Difficult and poorly studied areas (for example, sugar desert or impassible jungle) and were alone with a pencil and line. Mainly this happened during the so-called "race for Africa", when the colonial powers of Europe – United Kingdom, France, Belgium, Spain, Portugal, Italy and Germany – divided the continent to the zones of influence. Often, the guidelines in such cases became meridians, which are visible only on the map. At the same time, the demarcation (designation of the boundary on the ground with the help of columns) was not carried out in such cases. The result of such a coarse separation was cruel conflicts inside artificially educated states. The most striking example is the Federal Republic of Somalia, for many years plunged into the bunch of civil war. Now this country is divided into dozens of small territories warring. Ethnic conflicts are smoldering around the continent, most often they are exacerbated after the elections, when the authorities receive a representative of one of the people inhabiting her, which is not satisfied with the rest.
Another example of unnaturally smooth borders – the northern point of the bay of Aqaba. Here are the boundaries of four states: Egypt, Israel, Jordan and Saudi Arabia. This is a strategically important point, in fact, the "gate" in the Red Sea, which is undergoing important trading tracks. It is not surprising that the rulers of nearby countries did everything possible to get access to the sea.