Why do these implicits only work for single element HLists?

hlist_to_list.scala

implicit def hNilToList[L <: HNil](l : L) : List[Any] = Nil

implicit def hListToList[H <: Any, T <: HList](l : H :: T)(implicit conv : T => List[Any]) : List[Any] = {
  l.head :: conv(l.tail)
} 
  
hListToList("foo" :: HNil)
//res23: List[Any] = List(foo)

hListToList("foo" :: "bar" :: HNil)
//<console>:36: error: type mismatch;
// found   : List[Any]
// required: shapeless.::[?,?]
//              hListToList("foo" :: "bar" :: HNil)