An SD card slot is more than convenient, it's essential. It would be complete madness to have to buy a USB peripheral simply to transfer photos from our cameras.
I'd imagine the SD slot is not as widely used these days. By and large the number one camera people use are their phones. Much smaller segment that uses point and shoots or DSLR cameras. And if they do use those, the USB-C to SD card reader can be stored in the camera bag along with the charger and other peripherals. I can't image it's that much of an inconvenience.
While I never use mine, I don't think they should take it out. It's so thin as it is (as thin as USB-C), why take it out?