Unfortunately
@Mic****
it has a lot to do with nationality. Passing through immigration, even with all the relevant documentation, is not guaranteed.
The ability to support yourself aside, immigration can be concerned with a number of statistics relating to your country of origin/nationality including, criminality, terrorism, illegal immigrants, undocumented workers, to name just a few.
It is a sad fact that a large number of nationalities are not afforded the same freedom of movement as say a white guy from Cardiff holding a British passport. 😂
Look around next time you’re breezing through immigration unimpeded. You’ll notice it’s a privilege, not a given 😉