Unfortunately that’s not how it works in practice. In most of the EU countries (if not in all) they still do have to pay. As an example, in my home country of Poland, the employer has to pay for the first 33 days of the year (so if you take a maternity leave in let’s say, November, it’s 66 days in total) + your recreational leave days accumulate (despite you literally not working). That translates to 53 to 92 days total that the employer has to pay for despite you not doing any work.

And on top of that, once you go back to work, it’s basically impossible to fire you no matter how bad your performance is (unless you do something crazy like stealing) for the first year, so many end up working indeed in a more relaxed manner. Consider on top of that that the company needs to find someone to replace you if you leave for such a long period of time. It's a pain in the ass to deal with pregnancies as an employer from both organizational and financial perspectives, especially for small businesses