Conduit bending is one of the first skills learned by new apprentices in a commercial or industrial shop. They learn to use multipliers for 15°, 30° and 45° for offset bends. Most settle in on the 30° bend since the multiplier is 2. It makes the math very easy. However it makes for less than aesthetic appearance if the offset is less than 6". However 15° bends can stretch out the offset too far when making 3" or larger offsets.
As an apprentice, I learned how to bend offsets using a triangulation method. It did not require any math at all nor did you need to worry what degree you were bending. It made it easier to copy existing work, all you needed to know was the distance between centers on the two bends. A simple method, just make the first bend to any degree you want, lay the conduit flat on the floor, place bender handle along the section of pipe that was just bent, measure from bender handle (90° to bender handle) to the conduit the amount of offset needed, then make the second bend. We still learned the math methods. As a matter of fact we had small charts that had the multiplier for every angle and the multiplier for shrinkage. We used these when bending with Chicago benders or hydraulic benders. We could cut and thread rigid pipe before we bent it and it would come out perfect.
Bending conduit had become an art form. There was real artistry in making a quality job. Then price became the driving force in construction. Cheaper methods had to be sought. MC cable use skyrocketed. Fewer and fewer apprentices are bending enough conduit to develop a real style. The craftsmanship has been lost in favor of the bottom line. Even on jobs requiring conduit, it is still about productivity. Electricians can't take their time to do a nice, neat job. When was the last time any of you installed a large rack of conduits and used concentric bends? In todays marketplace you can purchase pre-fabbed 90° bends of 1/2" EMT. It might actually be cheaper to buy these factory bends and couple the conduit together than break out the hand bender.
It would be nice if we could turn back the clock just a little, to a time when electricians took more pride in what they did, when you wanted to take pictures of the work you had done.