Another compounding effect is that in order to get good at hiring, you need years of experience hiring, so you can find out what kind of interview is predictive and what kind of interview just wastes time. Most small companies don't have that kind of history to draw on.
Also, when you are able to detect and hire the best people you can put a heavy pressure on the competition by simultaneously depriving them of talent and attracting more talent yourself. E.g. if the company A that has 8 out of 10 top people in my field made me an offer then the B with 0 such people will have to make a much better offer for me to even consider them.
In such a situation the usual "false negative is okay, it cost more to hire a wrong person than to skip a right one" stops working. Skipping a right one will cost a lot in the long run.
