I'm not really sure about this because far too often I see ads for various services/courses/etc that I want to buy, but I don't end up buying because it's a subscription and I just don't have the bandwidth currently to spend time on the thing. I want to buy it and keep it on my shelf until I find the time to get to it, like a book.

And the price they give me from clicking the ad is a limited-time discount so then I'm turned off from ever coming back later and paying the full price i.e. the sucker's price.

Surely this isn't the optimal business model for many of the products that have adopted it.

You're not the average person. You probably also don't have significant credit card debt or rely on buy-now-pay-later for making purchases. Subscriptions are a win-win for the average company and user - users pay less upfront when evaluating the product, and companies can rely on a steady cash flow to continue paying for development and ongoing maintenance costs.

Every time I looked at customer spending graphs at my previous jobs, I realized how my habits have nothing in common with an average consumer. We’re extreme minority in most of the cases.