You skipped right over the hiring facts of: the face to face interviews, consideration, and most importantly, the option for the (potential) employee to exercise their choice of whether to take the job or not.

None of which is available to the employee in a 'fire by email' scenario.

you are assuming you know the content of the email. As others have said, severance and support programs could be outlined in the email.

I prefer email over HR walking past all the cubicles praying they won't stop at mine.

Because firing is a much different experience for employees than being hired? That should be obvious.

Having gone through many layoffs, there is no way to do it where it doesn’t suck for everyone involved (those that stay or go).

However, doing it in a way that show management understands the gravity of the situation goes really far in reducing how unpleasant the experience is.