A:Answer Are you referring to the 2.5" slot? The number one reason is the cost cutting by not providing that extra space. The second reason is that many people are skipping on the hard drives these days. And the third reason is that, if you really have to have one, you can always attach an external hard drive using one of the USB 3.1 ports.
I am with you that the 2.5" slot is handy because I have a couple of SATA SDDs that are not M.2 compatible. Unfortunately, the general trend is to skip on that slot in laptop computers.