Because they are afraid of changes, because in this case they will have to adapt to completely new conditions.
It sounds as simple as possible, but I also adhere to this point of view. Although, financiers are far from stupid people.
Many doesn't want to take new risk and always go to what they know that's why we see them oppose because they don't know on what's really happening also on what it can possibly offer to its user. But if they study how good bitcoin is for sure they will tell that bitcoin is good option in profitability also with as currency to use. For now since this is new to them maybe we should let them discover how big the potential of bitcoin is since for sure they will adopt it if the bitcoin demand will soar high more.