Cracks can come from building settlements, trees and vegetation draw moisture from the soil, different materials interrelate with each other the bricks grow (absorbs moisture) while shrinking concrete in time, termites and pests of wood, different materials of heating and cooling on different levels, and other reasons.
If you buy a house you are best to know why. But regardless of their knowledge, know that most inspectors are not going to move through a hole that is too small, and they will not move furniture, and they will not do invasive testing. If you are looking for buyer inspection then you can navigate various online sources.
That is, they will not dig into the wall, or try to get under the surface of the building they were checking. Usually, there are terms and conditions of every country. So, if this might have worked before the inspectors arrived.
When you bought your home, you want to know that it is what you think. You do not want to pay half a million dollars to find you then have to pay more.
Professional building inspectors also carry professional indemnity insurance and that helps you sleep. An inspector is not equipped with an x-ray vision. But this does not mean he cannot observe, and not be able to use tools, such as moisture meter to find a leak behind the shower and so on.
However, it does not mean that he cannot always really know what lies behind the surface of what he saw. What he has is the experience of decades, and it is that experience you call when you need help.
The money you spend may give you peace of mind. It will also provide information about the building so you can ask to have it repaired if it is a problem. As a social phenomenon that also keeps people honest. But in the end, it is up to you.