The obvious bottom line is about CCD sensors. CCD sensors can be used as shutters. CCD has to be disabled each frame to transfer the image out of it anyway, so they can simply time the enabled time as a shutter. Inexpensive cameras (compacts and camcorders, and less expensive DSLR too, back in the older days) still use CCD sensors for the free shutter. These have a cheap mechanical shutter too, to cover the sensor and keep light off of it, used for slow shutter speeds, but faster, has to be left open so the electronic sensor shutter can time it. The downside is the light is still on the sensor when disabled, which can cause blooming.
But the DSLR use CMOS sensors now, better, but more complex, much more issue to disable and reenable them (very slow to do). The first Nikon 1 cameras (mirrorless, NOT DSLR) were CMOS sensors, but had a choice, one model used sensor as a shutter, but its flash sync speed was only 1/60 second. Or a second model with more expensive regular focal plane shutter, with 1/250 second sync. Sync speed is related to shutter operation time, and CMOS is just too complex and slow. Compact users tend not to be concerned with flash sync speed.
The focal plane shutter is technically a much better shutter, but has disadvantages of expense, and of limiting flash sync speed currently to around 1/200 or 1/250 second. Just how life is.