Now a days, most of the institutions are organizing scientific conferences every year. Even in some countries it is mandatory to arrange such event. Of course amount of money spend on it is huge. How does this help?
Finding benefits from the scientific conference will depend on the person who's attending. A recently graduated student may sale his/er research idea and find his/er future supervisor. A continuous student may extend their network and establish potential research collaboration.
Conversely, it's more important for academicians to connect with global community and be on trend of research. Scientific conference is where people come up with their current/recent works.
And at the end, it's the best place to promote our research.
(This is how I personally view a scientific conference)
The scientific conferences with limited capacity of delegates and good resource persons are helpful. But mega events are utter wastage of money and time.