Having a bitcoin investment or not, one can still have an emergency funds for an unforeseen challenges that might arise in future and you need to prepare for it. Any investment that you venture into apart from bitcoin investment, an emergency funds is necessary so that you don't use from the investment to take care of real emergency when it arises especially when the investment is just growing. Some new investor starts their bitcoin investment journey with an emergency funds already in place before they know about bitcoin and decided to invest in it. For example, the rich and people that knows the importance of emergency funds.

Imagine when you have $10000 and you want to start a business, if you use the whole $10000 to venture into the business, if the business is not doing fine, you will not have extra funds to keep the business going because you used all to invest and forget to keep some to maintain the business incase any unforseen challenges that you did not consider befall on your business which might lead to run down of the business. If you use $7500 to invest in the business and keep $2500 for any unforeseen challenges in the business, when it occurs, you will get rid of it and your business will continue.

I guess that you wanted to say that when a real emergency occurs in future that is only when one should use his emergency funds and not needs. This is because we already know our needs and we take care of them whenever we get paid but an emergency is something that we don't expect to happen but takes us unaware and we must take care of it so that it does not lead to more losses or affects us in a negative way.