While every investors does need an emergency fund available for obvious reasons, you don't have to save up for emergency before you start investing, you can start with your investment first and then start saving for emergency situations later or you can do them simultaneously, and both funds should come from your discretionary funds so as to not disturb your necessary and basic expenses.
Emergency funds are like a fail-safe that helps to ensure your investment isn't disturbed during accumulation, it also makes provisions for situations like you losing your job, it helps keep an investor going until they secure another job and get their income flowing again all while keeping their investment intact.
I'm sure there are situations where investors had to sell the bitcoin stash early to take care of emergencies, it could be an accident and your insurance isn't coming early enough or it's not able to cover your expenses, it could also be a serious health condition that requires alot of money to treat, your emergency income accounts for and helps take care of these situations.