And you invested your time on a training, later surprised by the cost, but as you were invested timewise, you are more likely to pay.
From my experience, even with due diligence and setting up calendar event notifications, I've missed a few subscription cancelations I intended. On the other hand, whenever I use something free, I always proceed under the assumption it can shift to a pay for service/product at some point in the future of unknown cost and assess risk accordingly. I don't think I've ever been surprised by a fee or lost time investment because of this.
As far as one time purchases vs subscription charges, I think there's a better argument for this case. It should be made very clear up front during the purchase that there's a time subscription model and what services are or aren't included in that service. The model used in Google Play makes it pretty difficult to confuse what services are or aren't subscription based from my experience which seems reasonable (can't say I've looked into the details, just know I haven't been surprised by what is or isn't a monthly subscription).
Forcing all subscriptions to auto-renew doesn't fix this.
I've seen plenty of apps/services where the selling point is the fact that they _don't_ require a card for their free trial. And people renew their subscription because they've found the product to be worthwhile; not because they used it for 30 minutes then forgot to cancel.
If you're forced to go through a process to renew something, you're more likely to question why you're going through the process and if the service the process exists for still maintains value to you worth continuing payment for. Businesses are aware of this and attempt to avoid those situations. Minimize friction of revenue, limit any barriers for money flowing in.
It's very intentional and I've yet to see a good argument for trial-to-subscription auto opt-in that is not a strategic money grab based on a probability of unintended customers. Many decades ago, magazine subscriptions were notorious for this exact same predatory subscription lock-in model, even making it difficult to cancel (while incredibly easy to enter).
For example, CBS All Access had a free trial a few months back which had Picard on it. The monthly fee was nominal and it looked like they had a few shows I might like so I entered the free trial period. After finishing Picard, I tried a few other offerings from the service during the free trial and realized none of them were to my satisfaction. Therefore, I intended to cancel but forgot. Surprise, next monthly billing cycle I see a charge on my card.
So, if the point of the use case of a free trial period is to offer a free trial to evaluate a service and decide if you'd like to continue but prevent you from paying a fee to "test drive," then the upfront payment authorization fails at this for many people who don't instantly cancel the second they decide they don't or may not want the service (but aren't sure yet), or be sure to do so before the free trial ends.
All and all, I would argue the up front authorization free trial case often grabs a subset of the free trial accounts into a full cycle of payment. It also likely grabs those less attentive to longer periods of payment for services they're not using. So free trials are often crafted to prey on these situations, which I typically tend to avoid.
I know I got wrapped up with a few project deadlines for a few weeks and didn't even have time continue exploring shows before canceling. I'd completely forgotten I even had the service. I guess I wasn't being clever enough.
It appears more to me like opt-out recurring subscription is actually the model trying to be clever. These practices are largely business friendly, not consumer friendly.
There’s nothing unique about a free trial period in that situation.
Another alternative is to allow an opt-in subscription service with a free trial up front that doesn't automatically setup a recurring subscription you have to remove. A lot of services use this model, successfully.
You downloaded CBS All Access, they made you free trial member, you have no idea how much it costs. You may even don't know it costs
You started watching Picard etc, 1 week later, when new episode came, you logged in, you saw your trial has ended, subscribe to continue, lets say 20$ / month.
Apple is trying to prevent this behaviour, actually in comments one developer explaining they made similar flow.