Have been in deep contact with data centre and rental server offerings in the past, there is a crazy large amount of fraud going on, e.g. 2 hours for free means 2 hours free resource to DDOS.
You're basically describing the internet-scumbag use pattern - bounce around providers and servers using nothing for more than a few hours at a time and making tiny charges to (other people's) credit cards that won't trip fraud controls because they look like verification charges.
There are very very many reasons to prohibit exactly that type of usage pattern.