Annoyingly, Azure does have this capability! If your company is a Microsoft gold partner (there might be other requirements, I can't remember) then your Azure developer licenses comes with £100 free credit per month. When this money runs out, every service associated with that subscription just shuts down. It doesn't overrun, heck I don't remember even getting an email about it, they just stop until it renews the next month.
They just refuse to implement this system for non dev licenses.
That's exactly the same way that Azure for Students works, which is why I use it instead of AWS Educate (well, that and because Azure doesn't limit what services you can use your $100 on, unlike AWS).
They just refuse to implement this system for non dev licenses.