diabetes usually shows itself, hypertension is a silent killer though.
i'm not arguing against check ups, but I could imagine why they are not as effective as you might think.
i myself do not get checkups, i have insurance, but going to the doctors is a miserable experience.
First is trying to schedule a visit. Usually the earliest they can see me is 3-6 weeks away. when I have free time to see a doctor, thats when I need to do it. I dont know whats going to happen in my schedule a month from now?!
next, if I actually get the appointment, I am punctual and show up 15 - 30 minutes before the appointment. However, I dont get seen for 30-45 minutes after the scheduled appointment. This isn't just one time, this is E[X]. thats 45 minutes waiting with people who are coughing , sneezing, etc. after I see a nurse for 2 minutes and get sent to a room, usually thats another 5-10 minutes waiting in an empty room.
when I finally see a doctor, I am only allowed to talk about one thing. if its multiple things, I have to schedule another appointment. usually the doctor cant help with any of my ailments, I need to schedule an appointment with a specialist. usually another facility. unfortunately, I am not allowed to schedule an appointment with a specialist directly, I have to see my primary care first.