Technology

Yes and no. Airplanes are complex, the 737 max especially so. To check every bolt after every flight would be impossible, that would require every plane to be taken to a certified shop taken apart and inspected and put back together after every flight. There are inspection intervals and lots of scheduled maintenance that regular airline passengers aren't aware of. We only see the planes we fly on not all the ones temporary out of service for maintenance. These bolts would likely be checked during some scheduled maintenance but it seems that the bolts may be failing prior to the scheduled check, or they were never installed correctly. It's not likely a concern to passengers, the FAA (and most other global air regulators) requires all airlines to follow all manufacturer guidelines and recommendations within a certain amount of flights after an announcement like this. Also modern airplanes are very safe one missing bolt probably won't cause and immediate problem during flight.