In Catch a Pet, catching an animal is only the start. You use your lasso to grab wild pets, bring them into your collection, and build up your pen as you earn more money. At first, you might be happy to catch whatever wanders into reach. Later, finding a pet you haven't collected yet becomes a bigger reason to keep exploring.
Your lasso also matters as you progress. Upgrading it helps you go after rarer creatures, giving you something to work toward instead of catching the same types of pets over and over. Meanwhile, the pets you collect can generate income, which you can put toward further upgrades.
There's always another pet to look for in Catch a Pet. Some pets are easy to catch, while others take more work to get. You can keep catching the ones you find or save up for a better lasso and try your luck with rarer animals.