The loss of dance as ritual according to van der Leeuw

Dance has always been a large part of culture, especially from centuries ago.  Dance has always been a part of rituals and ceremonies across centuries.  However it seems as if this isn't as apparent in a lot of cultures today.  I think that dance as a ritual has decreased as years have passed.  It is still out there for sure, but I don't think it has the same implications it once did.  van der Leeuw writes "We have lost the dance as an element of culture almost completely, and so the graduation dance may strike us as somewhat ridiculous." (page 32)  This raises the question why has this decrease happened?