“and in some cases it is a good idea if your passport is not stamped by a country that you visit.”
Well, I have never been in a country that did not stamp my passport. The exception being in the EU, where there are no
longer immigration checks.
Even before the establishment of the EU one could travel between some of the N. European countries without an immigration check.
The problem with having your passport stamped is that while it may not be a problem for you to visit country B when you later must go to country C it could cause a problem to have a B stamp is your passport.
For example, my wife is of a certain religion and travels to a certain country every year or so.
For the purposes of my work, I have traveled to a certain kingdom that is located in the same general region of that country my wife like to visit.
The word is that if the wrong people in that kingdom were to see that I visited that other country, I could have some issues ranging from being kicked out of the kingdom to having a certain body part that is located in the same general region of my neck chopped off.