This is from the mpu6050 datasheet.
In the datasheet, gyroscope sample rate can be changed by frequency, but accelerometer cannot. Why this happens?
The table you showed in the question refers to the clock used to time the readings. You can't directly set that. That is automatically selected by the chip.
According to the datasheet (page 12,) the gyroscope can be set to various data rates between 4Hz and 8000 Hz.
On page 13, you can see that the accelerometer can be set to data ranges between 4Hz and 1000Hz.
I didn't see how to select the data rates in the datasheet, though there's a reference to a "MPU-6000/MPU-6050 Register Map and Register Descriptions document" that probably describes that kind of thing.