It's getting a little bit silly now.
You order something with Amazon (which is available and in stock) but won't be dispatched for around a week, simply because "free delivery" was selected.
It used to be the case where if you ordered something before 3pm, it would be processed and dispatched within the same day, no matter which delivery service you select.
But now, it seems the consumer is basically being punished for choosing the cheapest option and it seems Amazon are trying their hardest and best at annoying people into paying for delivery or signing up for Prime in order for them to be dispatched in a reasonable time.
tldr: Amazon are being extremely audacious and greedy by holding items for a week before dispatching them if you choose free delivery.