bloody good question I have always wondered this afterall gypsum board was invented to replace lath & plaster which was a real headache, I worked on a 600bed hospital construction in the middle east and all internal walls were steel studs and plasterboard with no plaster, the plaster boards were recessed to accomodate the tape and filler and was very fast and was ready for painting and or vinyl, a few builders wanted to apply 3 - 5 mm plaster which the consultant blocked and explained why, with steel studs the levelling of the plaster boards was next to perfect, he explained to me that with skimming it encouraged poorer workmanship on the studs fitting and the fitting of the boards which in many cases were very slip shod especially with timber studwork, consequently plasterboard was poorly handled and often broken which required plastering, the consultant showed without skimming the walls were flatter and this could be shown by shining a light at an angle, many builders disagreed but i found the consultant to be right, I explained why are they so for skimming he said you cant teach old dogs new tricks and its also jobs for the boys, i found all this very interesting ive looked at the arguments when plasterers say a skimmed wall is better but ive looked at it hard when I built my house in the philippines i used plasterboard onto galvanised steel studs and 15 years later still looks as good as new, ive looked at new timber stud wall during erection and there far from level and with that they need to be skimmed which all adds to the time and the cost, but i suppose the saga will always continue
