The reason for this is because mama cats will groom their kittens while they feed nurse.

My cat used to make sure she got my attention before she ate from the bowl next to my PC on my desk and then would purr up a storm when I pet her while eating.

She would also sit in the bath tub and watch me the whole time I was in the bathroom and then sleep on my pyjama pants that I tossed on the floor when I showered.

I miss that little goober.