it can take at least a week (sometimes more) for the E-check to clear. My bank needs a good 5-14 days to clear & send e-checks. If it bounces, the seller is looking at at potentially another 1-2 weeks on top of that to rectify the situation with the buyer, depending on how diligent the buyer and his bank are. Holliday weeks further bog things down.
With direct credit PP transactions theres zero lag-time. You can have the payment in your CC acct. in 5 minutes, dash off to the local PO and have the item shipped the same day of buyer payment.
Many times customers are impatient (borderline unreasonable) and want their goods ASAP. With e-checks you are at a higher risk of negative feedback for slow shipping.