I get questions often as to why I'm not checking for XYZ cancer and there's a few answer to that. There are basically 4 answers as to this (there are whole fields around this and I'm going to try to give you the 10 cent answer so apologies if I gloss over details and keep this more general)
WE DON'T KNOW HOW TO SCREEN FOR IT: In order to successfully screen for something, it has to be common and you have to have a good way of finding it in people who feel totally fine without doing a lot of damage to those people. Think of trying to find coins - a metal detector might be good at the beach. Not so useful if you're just roaming around the desert - it'll take you forever to find anything. Not so useful if you're on land with tons of old screws and washers and things scattered about - too many things you find that you're not interested in. This is the category that pretty much every cancer falls into except for Breast, Cervical, Colorectal and to a lesser extent prostate, some skin and testicular, and liver and lung in a few people, just based on how common they are and how good our methods of detecting them are.
YOU GOT CHECKED TOO RECENTLY: Once you do start cancer screening, there is an interval between tests. Why do we check every 2 years instead of every 1 year and 11 months? This is based off of anything we've found previously and all the research that goes along with it and the arbitrary intervals set up in the research studies. Checking more frequently doesn't help most people. Again, there is this balance between doing harm by checking too much and the benefit of catching things early.
YOU'RE TOO YOUNG TO BENEFIT: Usually, your cells need to be dividing for a long time before they start making mistakes that lead to cancer. You haven't been around long enough for that to happen with regards to XYZ cancer. The chances of finding XYZ cancer in you are so low that you are more likely to be harmed by the way we check for it and that goes against the "First, do no harm" part of doctoring.
YOU'RE TOO OLD TO BENEFIT: The older people get, the more likely they are to have harm come from the cancer screening methods.
Getting past that, the goal of cancer screening is the idea that if we catch a cancer early, you will live longer and with a better quality of life than if we find it when it starts causing you problems you can feel (symptoms). For a lot of cancers, the time between when you get it and when it starts causing symptoms can be many years, during which time there's also a good chance of something else happening to you (if not cancer, heart disease, infection, or accidents are what have gotten most of us since the dawn of time) so you wouldn't even benefit from the screening and any procedures or treatments that would result from it. It's also not assured that our treatment is any better if we catch it early vs catching it when you have symptoms.
Past that, let's say you get screened and find out you have the cancer. If you're otherwise feeling well, most people are going to want to do everything they can to get rid of the cancer which usually falls into chemotherapy, radiation and/or surgery. We've made great advances in all these fields but they are still very intense and far from risk-free. The older people get, the less optimally your organs function and the more likely to have bad things happen with all of these treatments. High enough that in many cases, they can make it so that you are more likely to die sooner from the treatment than from the disease.
These are the reasons that every type of cancer has an age where we generally stop screening for most people - it just comes down to the lack of benefit people get from it.
BUT I KNOW A GUY WHO HAD BACK PAIN AND THEN FOUND OUT HE HAD PANCREATIC CANCER AND DIED 2 WEEKS LATER: It happens. It's terrible, but that is just how it happens some times. Some cancer grow slowly and some grow very quickly - there is no good way of catching something early when it spreads too fast. These are the stories you actually hear about so often because they do make us look at our own mortality and our society tends to prioritize negative stories about inaction over anything else. There are plenty of stories of people who survived XYZ cancer and plenty more that you won't hear about complications from biopsies and treatments that may have been unnecessary to begin with because those stories are not things people like to talk about as much.