As a counterpoint, I found that Google had deleted all my servers from the GCP trial. I thought it's like AWS where it automatically starts billing you at the end. In fact was pretty sure I was paying for them (Google is definitely sending me strange unmarked invoices for something) but it turns out you have to activate it manually, and when I didn't, they just nuked the whole thing.

I disagree, because this would force all services to store the time of your last activity, even if they don’t want to track any such data for privacy protection. In addition, it would be prone to accidental cancellations losing you an important account, or the service could just claim you didn’t click the renewal button if for example they want to get rid of unprofitable customers (if you don’t use a service you also don’t generate ad impressions, or similar), which is difficult to disprove after the fact.

How hard is it to check your monthly bank statement and see if there’s anything unexpected? One normally should do that anyway.

The immediate second order effect of such a law would be to raise subscription prices on everyone to account for this automatic churn.

I would wager that most people who aren't watching their bills closely enough to notice they haven't actually used their Netflix account in a year aren't very price sensitive. They have money they are, by revealed preferences, willing to throw into the pot, which lowers the service cost for everyone else who does actually use it. If anything one should be the least sympathetic to their plight, from a welfare angle.

The business model you're actually looking for is a utility, or a pay-per-use model. Getting charged per API endpoint hit, or by TCP packets sent, or something. A subscription service is explicitly designed to avoid all that, because our brains like nice round predicable numbers. Sophisticated users everywhere use this model, but most of us have better things to be sophisticated all the time.

If something is to be considered insane, it is to demand a law for this. Mind your business – used to be written on the currency. If I buy a chicken and leave it in the fridge without eating it, should I also demand my money back from the supermarket?