Regular dental check-ups allow your dentist to spot signs of any dental problems early that you may have ahead of time (even the silent ones!) and nip it in its bud. Leave these to deteriorate, and you may get a toothache, need costly and invasive dental treatment (e.g., a root canal treatment, extraction, or dental implants, etc.), or even worse, risk losing your natural teeth unnecessarily.
It is well proven that patients who regularly have dental check-ups and visit a dentist every six months are far less likely to suffer from dental disease than patients who attend sporadically or solely during dental emergencies.