That's a pathology called "non event feedback", just because you've avoided catastrophe with risky behavior in the past doesn't mean that the risk doesn't exist, it just means you've gotten lucky.

Why change wikimedia's method of fund raising and budgeting? Because wikipedia is a valuable resource and it would be far greater if we could ensure it remains available for reading and continued revision not just for the next year or the next decade but indefinitely. They've already raised enough money to have ensured that had they invested the money correctly. Instead, the money has been squandered on salaries for positions within the foundation which provide questionable value.