Could this be a bad thing to refuse sealants?

Could be: Dental sealants provide a physical barrier so bacteria can't sit in the pits and grooves on the chewing surfaces of teeth and make cavities. Bacteria digests what we eat, particularly carbohydrates, and produces acids that make cavities. Studies have shown that when small cavities are covered with dental sealants, the bacteria are "starved" and can stop the cavity from getting bigger.

No: It's like refusing an optional insurance when you are renting a car. You have the right to refuse any treatment, including sealants. Sealants are placed in deep groves of posterior teeth, to prevent decay. Usually sealants are preventative, and thus covered benefits of dental insurance so most people will accept treatment for their kids.

It could be: Sealants decrease the chance of developing cavities. So, you would have an increased chance of having a cavity on the biting surfaces of your teeth if you don't have them.