Why PCB manufacturing time has 2 options ?

I find a problem where ordering a simple PCB cost you around 25 USD$ for a start, shipping not included. When ordering PCB it gives you only 2 options for PCB manufacturing times:

• 24hours with a cost of $25.71
• 12hours with a cost $111.73

Why this option is forced for buyers ?

Sometimes we do not need such a fast delivery so any other option is welcome .

For example if you order and want your pcb to be manufactured in 3-4 days you can pay less for it, let say less than 10 USD$.

It would be fair enough for somebody who is not in rush.

I would like PCBWay to consider this option and add additional options to it's manufacturing times so people could choose their priority of manufacturing pcb.