If people put the effort in to look after their teeth, the majority of people wouldn’t need to see a dentist any more often than once a year. (This is on average. Some will need twice a year. Some every couple of years).
The fact is, a large percentage of the population just do not look after their teeth that well. Some people just will not do what is advised. They refuse to floss or use interdental brushes. Will only brush once a day. Often just with a manual brush. Some people lie about what they do. “Yes I use my interdental brushes daily” as you look in their mouth to see a solid wall of tartar that has covered all the gaps totally. So how are you getting it in between when the gaps are 100% clogged up? Some people just really struggle with the dexterity needed to look after teeth well. This is definitely the case in young children and some older/elderly adults or those with some health conditions.
Diet plays a big part. Frequency of snacks/sugar etc rather than how much. Obviously drinking a litre of coke a day is not good for you. But it’s much better (for your teeth not your health) to drink that much with say dinner only then put it away. It’s actually worse to have a can of coke on your desk and sip it constantly throughout the day. So it’s better to let children have a treat once a day then give them a bag of sweets and ration them over the day. Giving them one sweet every hour is much worse than just eating the bag after dinner.
Luck and genetics definitely play a part. You can absolutely have someone who spent a large part of their life smoking and eating crap and only brushing once a day with no interdental cleaning etc up until 40+ and have no fillings or gum disease (looking at my husband….). And some people will be much more prone to issues despite looking after their teeth.
Gum disease especially is one of the worst things and the most common things. It can be totally painless. And especially if you smoke can have little bleeding. The first you might notice is your teeth getting loose. This is much worse than dental decay in the long run. With decay you have options. Fillings, crowns, bridges, implants. With generalised gum disease if you lose all your bone, the teeth WILL fall out. It’s incredibly hard to stabilise and there is no cure. No easy fix like fillings.
So I highly advise everyone gets into a routine of bruising twice a day, ideally with an electric brush (although this is not essential if you do do a good job with a manual). Clean in between your teeth once a day at least. (FYI- no one’s teeth are all too tight for any kind of interdental cleaning). Ideally ask a dentist or hygienist what would be best for your teeth. They can also show you the right technique. Stop smoking or vaping. Reduce the frequency of sugar. Those are the basics at least to help.