Because then you can do business in the US (largest English speaking client base) without any trouble?

And accepting debit cards (especially US cards) is still quite hard in most of the world afaik, aside from the UK, so this is a godsend to any entrepreneurs who want a real chance at success.

This was actually the dream just half a decade ago, to incorporate in the US without having to actually get a visa and go there and easily conduct business with anyone in the world...

Nowadays, it's not as pressing, but still a great service imo...