5 hours ago, stouricks said:

How much time does it take an Immigration man to put a dated stamp in a passport, directly after the last one, so that the person's movements can be easily seen. 5 seconds?

The problem is not where Immigration put the stamp, but the fact that in many countries they don't put any stamp. Take Europe by example where Europeans can travel in all EU country without any stamp.

America doesn't stamp passports on exit. Hong Kong and some other places now give out small loose slips on entry, and nothing on exit. Point is, with computerisation, not that much reason to actually stamp passports anymore. And the time it takes to place those stamps does add up when you're talking tens of thousands of travelers a day,

To many issues with a visitors origin and travel history. As has been pointed out, dual nationals could just use the 'best' passport for entry ( and still a problem if that is all you base it on). And of course many countries do not stamp you in and out. And even if they do, the stamp may show different languages (like Arabic), so you expect the immigration officer to sit down and work out which one is in and out, or even which country it is? Half of my passport stamps have no legible country on them..... The home country officer would no doubt recognise it, but elsewhere?

 

Countries like Thailand do have to profile and health check visitors. Those at risk should all be quarantined. UK was lax about who they let in (even during the peak of the pandemic!), Research has shown than Corona was imported on at least 1300 separate occasions in the UK (each causing a new chain of infection), and then you wonder why it got so bad.