In some European countries, PhD programs are free. As I understand, PhD opening depends on the research funds of the supervisor. In other words, PhD research is funded by a national agency or EU.
Some countries offer the programs for free and an international student in the UK should pay about $20,000 per annum?
In addition to the research cost (which is funded through the same routes), a PhD student has other expenses for the university, which is provided by the tuition fee in the UK, while in countries with free PhD programs, the governments provides the supports (correct me if I am wrong).
My question is: Why/how such governments support PhD education of international students? And if it is reasonable, why isn't it the case in the UK?