I suppose, one advantage would be that you can use it while almost asleep, while you need a minimum of mental presence for a shower. So if you wanted, you could: wake up; slump into the bathroom and into this thing; press the button; snooze another 15 minutes while part of your morning routine is being done for (or to) you.

Whether this is something you should do is another question...

(Also, it might be possible to extend it with hair washing if you mount one of those barber sinks at the top and then somehow automate it. Exercise left for the reader.)

Your vision lacks the ultimate destination: This will replace the bed.