When you pay from a bank account, you are writing an 'e-cheque'.
Although the money comes out of your bank account immediately, it has to clear the Canadian and US banking systems, before it can be released to the seller.
This can take up to 10 days. It usually is faster.
When you pay from a credit card, the money is transferred to the seller immediately. So he can ship faster and you get your purchase faster.
The other poster was referring to Immediate Payment Required items, which is common on Fixed Price listings. Especially if the item is in a category with a high number of Unpaid Item Disputes. That includes makeup.
It also allows you to buy stuff you don't actually have enough in the bank for, on credit. Which might or might not be a good thing.
The credit card is anonymized and there is no more or less security having it with PP than your bank account information.
Finally, paying with a credit card gives you a third level of Buyer Protection. EBay, Paypal and your card's chargeback policies.