How rude and unhelpful. Why do you think OP is "looking for excuses??? And why do you think "Brush your teeth, avoid fizzy drinks and sugar" is in any way helpful given that OP clearly states she doesn't drink fizzy drinks and brushes teeth regularly?
Yes, lifestyle matters. A lot. But as others have commented, some people can have quite poor diets and poor oral hygiene, and still have good teeth (I think most of us know at least one person who eats lots of sugary foods and still has good teeth). Some people have good diets and good oral hygiene and problem teeth.
Thats because there are many factors that impact dental health.
Genetics.
Childhood diet.
Tooth and enamel strength (because not everyone has strong teeth -this isn't an 'excuse", it's objective biological truth);
hormones (pregnancy, menopause),
other health conditions (sjorgens, osteoporosis, dry mouth etc)
medications (eg asthma inhalers, which the OP uses,. Also antidepressants, antipsychotics, chemo/radiotherapy, epilepsy medications, etc.Clearly from your comment you've never experienced medication induced dry mouth. Hope you never do, because it's really grim, and it seriously effects your teeth).
Composition of saliva (impacts remineralisation),
immune response (some people can have quite a lot of plaque on teeth and have only minimal inflammatory reaction of gums, others can have more pronounced inflammation with very little plaque).
Lots of factors. Yes, diet and brushing are important - but it really isn't as simple as that
And there lots of reasons why someone might not get to dentists regularly. Anxiety, depression, sensory issues etc. no idea of that's true for the OP but there's a fair chance it's true of at least some people on here.
Making overly simplistic, unhelpful and judgemental comments (like "stop looking for excuses and brush your teeth") adds to shame and anxiety that people with dental issues feel, and makes it more difficult to get to the dentist.
Honestly. Engage your brain before you comment!