Since cotton holds vapour, ie. it doesn't wick, then it is not a great choice as a base layer either in the cold or the hot weather conditions you may be walking in, that doesn't take into account whether you sweat ( sorry ladies, glow) or not.
It is however a reasonably easy to source and cheap alternative to polyester or merino, or the newcomer to the wicking scene bamboo(or other plant based cellulose), which is why companies still produce it, not for its capabilities as abase layer but it potential asa profit maker.
Better technical reasons behind not using cotton can be found in this forum using the search function.