PhD students do useful research work. Supervisors will want a PhD student who successfully completes a project. A candidate who already has a PhD may be more likely to quite prematurely. I've seen it happen.

When I did my PhD, a new colleague PhD student joined. He already had a PhD from a developing country, from a university that is perhaps not very well known outside his home country. He considered that a PhD from a more established university in a more developed country would be more valuable.

Fast-forward two years, he suddenly left when to take up a postdoc position in yet another developed country. His supervisor was not happy, and I expect will think twice before accepting again a PhD student who already has a PhD.

PhD students do useful research work. Supervisors will want a PhD student who successfully completes a project. A candidate who already has a PhD may be more likely to quit prematurely. I've seen it happen.

When I did my PhD, a new colleague PhD student joined. He already had a PhD from a developing country, from a university that is perhaps not very well known outside his home country. He considered that a PhD from a more established university in a more developed country would be more valuable.

Fast-forward two years, he suddenly left when to take up a postdoc position in yet another developed country. His supervisor was not happy, and I expect will think twice before accepting again a PhD student who already has a PhD.