Q:

Is there a reason beyond the simple textbook explanation as to why the Allied forces chose to fight the Axis powers in North Africa during WWII?

The textbook explanation is simply, "colonialism". But I'd like to understand the more profound motivations for the North African conflict. Ultimately, what had the Allied forces to gain? What motivated the Axis? It just seems deeper insight is often left out of a lot of war narratives which often tend to focus on merely the strategy and tactics used for the war instead and only lightly touch the  motivations behind the war--or they simply give blanket explanations like, it was just due to their "colonialist" ambitions. 

A:

The Axis fought in North Africa because the Allies attacked them. No particularly deep analysis needed there, although it's worth mentioning that, unlike the Allies, the Axis forces never simply retreated in the face of overwhelming strength. Why they always fought an attack even when retreating would be strategically better is an interesting enough question, but the answer has nothing to do with North Africa in particular.
Alan Brooke's diaries provide a practical perspective on all this. The Allies reasoning for the attack on North Africa was:
1) If we can't help the Russians in their fight on the Eastern Front, they will lose, and Germany will become impossible to defeat.
2) We need a second front to draw troops away from the Russian front, and give the Russians a chance to beat the Germans there.
3) We can't attack occupied France yet, because there are good east-to-west rail links across Europe, and the Germans will be able to bring the first reinforcements to France within hours of our attack. And once they've dealt with our attack, they'll be able to go straight back to the Russian front.
4) On the other hand, Europe's north-to-south highways and railways are relatively poor compared to those going from west-to-east. If we attack Italy, the reinforcements will arrive more slowly, and won't be able to return to Russia as quickly, either.
5) We can't sail all the way from Britain to Italy with troop-ships, warships and aircraft carriers, because it's too dangerous and we would need to carry a huge quantity of supplies.
6) In order to attack Italy, we need military bases close to Italy. So we need take North Africa from the Germans and Italians.
In addition to 6), the Allies wanted to attack North Africa because many of these areas were French colonies. The Free French forces wanted them back. The allies wanted the Vichy French authorities to stop sitting on the fence, and force them to fight the Germans.
Moreover, the Allies wanted to reopen the Suez canal. Axis control of the Mediterranean meant that Allied supply ships had to take humungous detours around Africa. Once North Africa was retaken (and Axis naval bases in North Africa had been captured by the Allies) the Allies were able to turn those ships around much faster, which meant more supplies could be taken quicker.

A:

The Axis were in North Africa almost by accident. Germany got involved (using Rommel), because the Italians bungled the invasion of Egypt. Also, the Allied "Torch" landings caused the Germans to occupy Vichy France, both in Europe, and in Africa.
You can allege that Italy was in North Africa for colonial reasons. She had conquered Libya and Abysinnia (Eithiopia) and conquering Egypt was to connect the two. But Germany had no interest on African colonial possessions because she had a much bigger "colonial" project going on in Europe.
On the other hand, the Allies felt the need to contain further Axis expansion. They could do nothing about opening a second front in Continental Europe, and only a little to help the Russians through "Lend Lease." The real fear at the time was that the Germans would defeat Russia and completely dominate Continental Europe.
So the Allies wanted to get a head start on "Round Two," which would have been "the world outside of Continental Europe." Africa had important prizes; one fifth of the world's land area; one twelfth of the world's population; rich natural resources, particularly oil in Nigeria and chrome in southern Africa.
Also, the American army needed a chance to test its wings against the Axis, without facing the brunt of German power. Africa was a good place for such a trial heat. "An Army at Dawn," by Rick Atkinson, makes this point.
Basically the North African campaign served much the same function for the American army as the Battle of Trenton did in the American Revolution. It offered the chance for a green American army to pick off (with British help) an overextended enemy army, and led to bigger and better things. It was a huge morale booster when American morale needed boosting, because it broke a string of Allied defeats. (The landings in North Africa preceded the surrounding of the Germans at Stalingrad by a few days).

