In the time you speak of someone who declared himself the King of the Castle could sleep with your wife at will, confiscate your land, put you in prison for no reason, or just exile you to some far away place by force because they didn't like what you say.

You can't have it both ways.

When relatively few people had the means to travel to other countries, it was not necessary to regulate them.

It's hard to believe now but, until the early 1960s, there were no restrictions on Commonwealth citizens coming to the UK to live and work.  Of course, citizens of Russia, Poland, Romania, etc. were not permitted [by their own governments] to travel to Western countries.

How times have changed !

yes,  times have changed, and the earth village going to take a while, how can we do?  when i was child, i always hear people can go any kingdom with a horse, have a wife in there:), yes that is just story hahahhh 

I feel that the reason is mostly that rich countries want to protect their wealth, and people everywhere want to preserve their culture.

I think/hope we'll get to the global world eventually, but it's going to take a while...