Yes, it happens a lot. Maybe it is to generate more profit, but I also know, that books translated in German need 15-20% more space and pages than in English for example. The first book of "A Song of Ice and Fire" would have more than thousand pages in a paperback, so I understand, why they split each book in two parts.

Here in New Zealand (and probably many other countries) we get each book in Brandon Sanderson's Stormlight Archive split across two volumes. At first I was neutral towards it, but due to circumstances beyond my control, I ended up with the fourth book in just one volume. This thing is gigantic! I'd find myself having to read in much shorter sessions than I normally would due to my arms getting tired. In the end, I had to switch to the ebook for purely ergonomic reasons.

I think I did end up paying more for the books that were split up, but to me it's worth it. I understand that won't be everyone's experience though.

A lot of books get split in English as well simply because they start hitting the limit of what print publication can do.

Most famous is probably the Lord of the Rings, split into 3 books, and Clive Barker's Imagica, split into two.

I think the English language versions of 3/5 ASoIaF books are already split into two anyway. Can't remember if aGoT or CoK are however.

I noticed this with Peter f Hamilton's Commonwealth universe books. The french versions all have more books and it confused me.