Why do the more popular search engines favour regionalisation? Because localised results are more popular with users.
If, for example, a search engine user is looking for a ‘route planner’, they would most likely want one for their country. Results for another country would be secondary.
Another regionalisation example –
Google.co.uk top search results for ‘buying a car’
Autotrader (UK), fish for cars (uk), buyyourcar (uk)
A search engine’s primary function is to produce search results that are relevant to the user; otherwise the user would quickly move on to another search engine. You can see from the above results that Google favours regionalisation in its search results. This is because results for cars in ‘Peru’ or ‘Australia’ are not particularly relevant if a user is in the U.K.