1. Baniya style businesses.
Though the startup founders are young and fresh, the overall business environment still reeks age old business patterns. I know few startups who offer no equity, treat employees like 2nd class citizens and want to get rich quick without spending much.
2. A lot of talent is ignored.
Everyone knows that the education system is inadequate for training engineers, but startups seldom train/intern students and bring them on par. There is a lot of latent talent apart from the Engineering graduates. Millions of students graduate as B.Sc.(Science/Maths) but I haven't heard any startup training/hiring them. Outsourcing giants like Cognizant/Infosys however are an exception but they hire, train and turn these non-engineering graduates into maintenance drones.
3. General apathy of students towards startups.
Most of the students just want to earn money to be self sufficient. The easiest way? Follow the patterns of someone successful, mostly a person selected in outsourcing giants. These companies are a modern version of dusty Government offices and many people just log their time and get a paycheck. Art of computer programming is forgotten and everyone wants to be a Manager/Director is 5 years. This sets a wrong example for new guys and hurts the hacker culture.
P.S. Many startups are doing good work (e.g. Infinitely Beta) and many will succeed, but these factors show why hiring is difficult for startups.