Some times just brushing isn't enough. speaking for myself I have Gastroesophageal reflux disease (GERD), the stomach acid eroded all my teeth and plus I'm a chain smoker which didn't help matters.
I hate my dentures, I have them out way more than I have them in. I wish I can afford implants, for a full set it can easily be $20k or more. Too bad I wasn't close to Mexico because implants are hell of a lot cheaper there than in the states.