Why does cricket allow for players to play for more than one country?

There have been many players over through the history of cricket to have represented more than one International team. The latest of these players seems to be likely to be Luke Ronchi. The wicketkeeper has represented Australia in the past, although not many times. He has now been selected for the tour of England for New Zealand, the country of his birth. 

I find it very odd that players can still change from one country to another, this is something that cannot happen in football. The rule in football (as it should be) is that if you have played senior international games for one country then you cannot play for another. Does Luke Ronchi feel anything for New Zealand? He did pick Australia over them before so why now does he want to go back? The answer is that he cant get in the Australia squad any more  therefore to play international cricket he has chosen a new country. This shows no real pride in playing for his country. 

There have been a few players who have switched countries in the past, but for most of them there has been good reasons for this. There are three players who have represented India and Pakistan. These being Amir Elahi, Gul Mohammed and Abdul Hafeez Kardar. All of these played for India before independance and later went on to represent Pakistan after partition of the countries. Iftikhar Ali Khan Pataudi played for England and India. This was in the early 20th century and should not really be considered as India were part of the empire at the time and there were no real cricket rules on this issue. 

There are many others who have played for minor cricket nations and then switched to bigger cricket nations. The latest two would be Eoin Morgan and Ed Joyce who went the other way. Others on this list would be Kepler Wessels who was captain of Australia during South Africa's ban from sport. He later went back to his birth country when they were re-instated. In my opinion these type of moves seem to be acceptable, but to move between two established cricket nations solely because you cant get into the team is not. 

I understand that countries may take players from other countries and naturalise them, for example there are alot of South Africans in England and Australians in New Zealand. But once a player has been played for the national side there should be no switching. If this rule is not changed it could technically allow a player like Kevin Pietersen to go play for South Africa one day. If England didn't accept him back into the squad after they dropped him he could have done this if South Africa agreed. 

I have nothing against Luke Ronchi but I don't believe he really should be allowed to change his country this easily.