When I started off, I wanted every user who came to my site to convert to a paying user. Over time, I realized that I actually didn't want for every person who showed up to become a paying user, because I spend more time dealing with issues that they bring with them than writing new code or adding features.

After you've been running businesses for awhile, you start to realize that the goal should be to get a specific type of customer (not every customer is a good customer for you, some types are a bigger drain on support resources than others), and the easiest way I've found to get those is to require a credit card for the trial. That might mean that I have less users overall, but I end up with the ones that I want.

I'm also not talking about saving on literal costs, necessarily, It's more about opportunity cost. I could be dealing with a ton of free users, or I could be dealing with a self-selected group of paid users and work on new projects. As a developer, a couple of hours here and there could potentially turn into a new product.