Now the following may sound obvious, but I don't think people lay this out as simply. Why is this speaker presenting at this conference?
#1 The person is selling you their company, product, or service.
#2 The person is looking for a new job and getting their name out there and what they do gets them known in the industry.
#3 The person is passionate about the topic and wants to tell the world.
#4 The person has done a great job and as part of the reward gets to speak on the achievements made.
In general as most industry conferences, I would say 80% of the talks out there are category #1. That leaves 20% for #2, 3, 4. And out of the 20% maybe 25% are good talks. So there are 5% of the talks worth seeing. Huh, maybe that's why I get so bored attending most conferences, and spend most of my time in the hallways networking.