The world might have become a smaller place in the past few centuries but it still a place where geographical boundaries are strictly guarded and where entry into any country os governed by its own set of rules and regulation and everybody without an exception, need to produce their passports which in most cases has to be supported with a visa.
Passports have been around for hundreds of years now but in the present times, a passport is not just considered as a travel document but also as a proof of the carrier's identity as well as his nationality and the address at which they reside.