Besides making the smellables unattainable, hanging the bear bag difusses the smell, making it somewhat harder for animals to pinpoint its source. There are bear-resistant canisters available, but bearbags are generally more practical for backpacking. Putting food etc., in cars is not an advisable alternative because bears can easily rip into a car. Although you want to avoid low ground, you may want to avoid the tops of bald hills when there is the possibility of lightening. Ticks may transmit Lyme disease.
Rodents are a primary food source for snakes, which are known to snuggle up to warm objects.
Most modern tents have good ventilation when the rain fly is left off on warm dry nights. But, if you aren't following safety pecautions, and insisting that those with you do likewise, you are putting yourself, those around you, and those that follow you, at risk. Our scoutmaster tells the story of a nephew's tent being visited at Scout Camp by a bear wanting to share his chocolate chip cookies. The moral is not that you should fear bears, but you must respect them. Bear in Advisor, Asst.