Materials are constantly being improved. Higher strength materials are available such that the wall thickness can be reduced without the disadvantages of poor weldability that one encountered in the past. As the thickness decreases, so too do the requirements for excessive preheat, special procedures, post weld heat treatment and the fabrication costs also drop.
Advances in welding knowledge contribute to improved fabrication procedures. Better electrodes or other welding consumables provide adequate strength to match the newer pipe materials and also the ease of use of the newer electrodes ensures that, in the right hands, there will be fewer welding defects.
All of these factors combined in the right welding procedure can satisfy the most onerous of modern specification requirements.