What is the real advantage of a NVR ?

user_951254242668760

Hello all,
I have installed 4 Reolink external cameras around my house, each equipped with a 256 Gb SD card, and I am quite happy with the Reolink app installed on my smartphone. The 4 cams are connected to my router (PoE). The parameters options that I can select for each cam, either with the application on my PC, or directly from the smartphone app, are really fine for me (sensibility of cameras, all types of events registered H24, emails and alarms sent only for human activity, ...). I thus can get direct alarms each time a camera detects human activity on my property (activated during night only or when I am away) and the 256 Gb cards enable more than 10 days of rolling history, which is more than needed in case of incident (the cameras are located ~6 m high, so no risk that an unwanted visitor will remove the cards ...).
I wonder what would be the additional functionalities that I would get by installing a NVR ? I even suspect that it would introduce a single point of failure in my installation (NVR down --> nor more video at all).
With such an efficient system (cameras + SD Cards + apps), I don't really see what I would get more with a NVR ?
Thank you for your advice.
Bruno (France)