We just had a thai coach (son yodyut) over for three months and the he spend lots of time emphasising footwork and foot placement stuff, same stuff happened when i trained at sasiprapa in BK last year. Again if you dont now what your looking at in a thai fight you might be missing the footwork aspect as it is much more subtle to boxing.
Its best done early in training other wise you will be correcting bad habits later on, and whe you get it down it makes everythig else easier. (in some ways footwork in striking is the equivalant to positions in grappling, you dont get the footwork down in striking your positioning and striking will be off, you dont get the postions down in grappling your submissions will be practically useless) Good work is the foundation for effective, efficent striking and makes a difference to timing of shots which might be the most important aspect of striking.
Other way to think about it is if you get two guys fighting one with really good footwork and one with inferior footwork, the one with footwork can out position and land more shots while taking less.