The service isn’t free forever, they’re just providing you with a free trial.For example, I just signed up with a service a couple of months ago where the 30-day trial period had a full feature set of their specific service.That's because our approach to Russian and Nigerian scam is different than on other dating services.
If you’re required to give a credit card it’s also a good sign that what you’re signing up for perhaps isn’t free forever.
If you think the offer might be legit, read all of the information on the screen carefully.
That prevents people from creating multiple accounts to do things like game a system, gain unfair access, or apply unfair weight in whatever that system is doing.
I’ve also seen scenarios where sites use credit cards to validate age.
When in doubt, always assume anything that says free but requires a credit card is a scam.