The reasoning why OSF-IT lost the IRST that the first generation OSF had was due to budget (and political*) constraints, and the Rafale was designed to be able to user the on-wing MICA IR's heads as backup IRST so it was easier to justify ditching the IR part of the OST than the TV side. It's not so much "doesn't need" as "can do without if it must". A return of the IR side was always planned.So IRST been under testing on f4.1 will be upgraded in f5 version. I do remember Rafale guys used to argue ( in a foreign forum, from our western neighborhood ) that Rafale's TV camera is so superior than the IRST and the bird doesnt need any such systems.
* The first generation OSF had been a compromise between France's two main electronic companies, Thomson-CSF (now Thales) and Sagem (now part of Safran). Thomson got the TV part and Sagem got the IR side. This allowed to preserve jobs and skills in both companies, but had the drawback of making things more expensive. That's why OSF-IT was contracted only to Thomson. In 2012, Thales and Safran created a joint-venture (called Optrolead) so now it's a single company that does both sides of the OSF.