Stamping is not a must. These days technology is catching up fast, everything is recorded electronically. The moment you, airline or the passport control officer scan your passport, the job is done. Stamps are a mess, though it looks good it consumes space in passport for frequent travelers.
I have traveled to all countries in Europe (as non EU citizen, holding residence EU permit), some countries dont even care to stamp, they just scan my permit or passport and wave me. It happened many times, but sometimes i get stamped the good old way :))
The bottom line is you dont need to worry too much about stamping, that is the job of border control, i am sure they know how to play the rules safe. All you have to do is just enjoy the travels, and rest will be taken care of :))
If you used an Automatic Passport Control (APC) machine, you will not receive an “Admitted” stamp. It should have been stamped onto the print out instead.
Admitted stamps are sometimes presented in US Passports by US CBP: Wikipedia is ever helpful: https://en.wikipedia.org/wiki/File:Us_stamp_2.png You can see that the “you must leave by” line has been left blank. However apparently it is not universal. You can ask if you want one.
See this web link for some more reports: http://ask.metafilter.com/205231/To-stamp-or-not-to-stamp
I am told by colleagues that it is helpful to have a stamp for filling out tax returns if you are domiciled outside the USA and wish to prove how much time you spend outside the US.
As US citizen you do not need a stamp in your passport, as you belong to the country. It is foreigners who need a stamp in their passport, as they can be asked to proof their right to be in the USA if stopped for whatever reason. Especially proof they did not overstay their visa and did not arrive illegally.
Most countries in Europe never gave stamps to their own citizens, nor do they give stamps to other EU citizens. As their citizens and those of other EU countries do not need visa and do not have limits on the time they can spend in the other EU countries.
Within Europe many, or even most, Europeans travel with their ID cards. Those do not have space for stamps. But even when I traveled with a passport I never received a stamp when traveling within the EU, or its predecessors. These days I keep a passport for travels outside Europe, and use my ID card for travels within Europe.
The Chinese border control people must have met more Europeans without stamps in their passports, even passports a few years old.
Credit:stackoverflow.com‘