Micro sd card readers =/= a micro sd card that you can put inside the phone. A micro sd card permanently attached to the phone via a USB-C card reader isn't really that practical, since it can easily get loose and you can drop it. I mean I can walk around and record videos directly into the sd card if the phone has the sd card slot.
A phone can get destroyed and I still have the video. Very useful for situations like... god forbid, if you ever get in a situation of being a witness to an act of police brutality and you are recording them for evidence, and they smash your phone after you recorded a video of them. And you then run away with the broken phone. As long as the micro sd card isn't damaged, the video is safe. Its much harder to recover a video from a broken phone's internal storage. And by the time you do recover it, you might not be able to send it to the press before cops show up at your door to confiscate it. In contrast, an sd card can just quickily put it in a computer then you email it to journalists.
I know, this is an extreme scenario, but like its just illustrates that a sd card plugged in to an USB C card reader isnt the same, it can come loose easily.