I guess I don't get it either. "Fixed price" is always a floor, never a ceiling. How is that good for you?

My power bill isn't the same every month. My water bill isn't either. I know my patterns and roughly the monthly cost, and I can use less if money is tight.

You know how much cellular data I use per month? 0KB. Why? Because I don't want a giant fixed price add-on to my bill. If I could buy a smart phone, use WiFi 95% of the time, and spend $5 on data once in a while when I need it, I would use some. But I'm not jumping on a fixed price. I'm not paying for more than what I use.