Having the availability to get cash during an emergency is indeed important. It does not have to be all cash, CD, high yield savings account. You can have US Savings Bonds. I have hundreds of thousands of dollars in paper iBonds and can go to my local credit union and easily cash them. The funds are immediately available....no hold.
Here's why credit cards are NOT emergency fund. If you lose your job, the credit agencies will post this. Many credit cards pay for information on credit reports. Don't believe it? I sell tradelines (thanks arebelspy) and I notice I get mail constantly for AU names at my address. Everything from collection agencies through SOFI refinance offers to AMEX and Cap One offers. So why's this bad? Well, that credit card that you're depending on to ride through an emergency can be cancelled. Then what do you do?
Credit cards may only be one option for an emergency fund. Always have contingencies.
Here's our overall emergency mitigation plan:
1. Live on one income (ideally the lower of the two spouses, but we aren't there yet)
2. Stable government jobs, so it's highly unlikely that either of us would be let go, let alone both (also means great health insurance)
3. Enough cash in bank for 1 month
4. Credit cards for emergencies that can be cash flowed within a month
5. Use bank churning money
6. Withdraw current year Roth contributions, which can be replenished
7. Withdraw prior year Roth contributions
8. Reimburse HSA funds that are available
9. Good family network
We don't make enough that we actually have taxable brokerages, but that would be a step if we did. Also, I would assume that many people are also willing to use a HELOC, if available.