It's a problem when businesses still have to pay the employee's salary while she is on maternity leave in addition to the salary of her replacement.
This is not true, the maternity is paid by the state. He mentions the high taxes as another problem, but in fact that's why they are that high, it's the same problem looked from the other side.
Also, there is a lot of productivity lost during the transitions.
It's common here, that women on maternity take a correspondence course or learn languages, etc. Often they are more skilled at the time of their return.
The law is like that because companies are much more powerful than the individuals. They have to take you back, that's fine, but still they can (and often do) offer you a position 300 km from your home, or exclusively in night shifts, effectively force you to quit.