Pondering gas appliances, why a flue on some and not others?

For a half century I have usually lived in places with gas appliances. So, I’m pondering gas appliances, why is there a flue on gas water heaters but not gas clothes dryers?

Dryers already vent to the outside. Would a second vent be redundant? (WAG)

Dryer gas is burned when the dryer is running, and it vents out the back.

Most water heaters vent out the top.

As the others have said, dryers vent the gas along with the moisture from the clothing. I’ve always wondered why we don’t worry about carbon monoxide buildup from gas ranges and ovens. Is there just simply not enough coming from it to be a problem?

when people use a gas stove/oven to provide dwelling heat they do die.

cooking is short term.

There are ventless, gas-burning fireplaces, too. They reduce oxygen levels, and add moisture to the air (by-product of combustion), and they vent right into the living space, and they shouldn’t be used for more than an hour.