Carriers battles in Pacific, but no carriers in Atlantic. Why ?

The British and Americans both operated carriers in the Atlantic and Mediterranean. There were no carrier to carrier battles because the European Axis nations never operated carriers. The Germans and Italians both started construction of an aircraft carrier (Graf Zeppelin and Aquila respectively), but those ships never became operational. The problem was you need more than just a ship to have a useful carrier, you need aircraft, trained crews, tactical doctrine, and logistical support. These take time and operational experimentation at sea to develop. The U.S., U.K., and Japan each spent over a decade developing their respective carrier air arms in order to have effective carriers ready for WWII. Germany and Italy started much later, and did not have their ships ready in time for sea trials before the war started. Once the war was underway, British and American dominance of the seas made it very difficult for the Germans and Italians to get their ships to sea where their crews could practice operations and develop a doctrine. So the non-Japanese Axis carriers languished in port with no planes to equip them and no trained crews to operate them.

But just because there were no Midway-style carrier battles in the Atlantic did not mean carriers were not used. The British operated several fleet carriers in various operations. On 11 November 1940 British carriers launched a raid on the Italian anchorage at Taranto. One battleship was sunk outright and two more were heavily damaged. The Japanese carefully studied every bit of information they could get about this raid, and used the information in the planning of their own raid on Pearl Harbor a year later. In May 1941 when the much hyped German battleship Bismark broke out into the Atlantic, the British carrier Ark Royal played a crucial role when a strike by her torpedo aircraft damaged Bismark's rudder, forcing her to run in circles. Unable to effectively flee, British forces gathered until Bismark was overwhelmed. British carriers were involved in several small naval skirmishes with the Italians in the Mediterranean Sea. Little damage was done, but the carriers did provide important scouting functions via air searches and inhibited Italian operations. Both British and American carriers were instrumental in ferrying aircraft to British bases in the Mediterranean, especially the island fortress of Malta, which sat astride crucial Axis air and sea transport routes between Italy and North Africa.

The Americans developed a new class of small carrier that became known as the escort carrier (CVE). These were much smaller (and slower) than the big fleet carriers, but proved instrumental in the war against the German U-boats, which was so crucial the campaign as a whole became known as the Battle of the Atlantic. Experience proved that enemy submarines were much easier to locate by search aircraft than they were from surface ships. And attacks by those aircraft, while rarely successful in sinking the sub, generally forced it to submerge and break off it's approach to vulnerable convoys. The CVEs provided air cover for convoys in the mid-Atlantic waters that were too far away from land bases for land aircraft to patrol. The U.S. navy eventually developed hunter-killer task groups independent of the convoys, each centered around a CVE, that aggressively hunted U-boats down and sank them.

Yes, carriers did figure a bit more prominently in the Pacific than the Atlantic. This was largely because the Japanese navy was far more formidable than the navies of Germany and Italy (excepting the very dangerous German U-boats). So naval battles in general were more prominent in the Pacific. It is also true that weather patterns in the Pacific were generally more favorable to air operations than the cloudy, stormy North Atlantic. But it is very much a misconception that "carriers were totally missing as a class in [the] Atlantic theater".