You generally do present your passport when leaving. Most places you get an exit stamp (which matches your entry stamp). They usually confirm things such as not

You generally do present your passport when leaving. Most places you get an exit stamp (which matches your entry stamp). They usually confirm things such as not overstaying a visa. ex: overstaying in Thailand results in a on-the-spot fine China lately has exit checks when traveling to SEA (they try to intercept people traveling to scam centers)