Because - to be blunt - it's not a serious issue. Speech dysfluency 100% sucks and can have outsized impacts on your life as someone who stutters (my stutter was severe for a number of years and I still deal with it today though to a lesser extent) \*however\* stuttering doesn't kill you, it's not destructive and you can live a broadly normal life with a stutter relative to diseases that leave a notable impact on a perosn (chronic pain, physical health issues, mobiilty issues, cogntive issues etc). Stuttering, big picture, isn't dangerous and the cause of it, whatever it may be, doesn't appear to do any actual measurable physical damage so it's not high up on the priorities list when we have deadly diseases requiring managements and understandings.