Question

why does hibiscus not bear fruits even though androecium and gynoecium present in it?

Answer 1

because is loses ability to produce seeds

Answer 2

while both tropical hibiscus and hardy hibiscus can be propagated from hibiscus seeds, typically only hardy hibiscus is propagated by this way. This is because seed will not grow into true parent plant and will look different from the parent. As it has loss it's ability to produce seeds so no fertilization will occur .This the reason that no fruit is produced..