It isn't necessarily that all astronauts are emotionless robots. It's just that both spaceflight and reality TV have specific requirements. The requirements of spaceflight are that you keep calm and do your job properly, lest you die.
The requirements of reality TV is that you've got an interesting cast who know how to play it up for the camera.
With reality TV- normal reality TV, anyway- you can switch the cameras off, you can stop everything and get help fairly easily if things go wrong. But this is incredibly high stakes stuff. It's almost like some sort of gladiatorial 'Hunger Games' entertainment- the intention might not be for the participants to die, but the threat of death in this case is pretty alarming.
And it isn't as if spaceflight is some 'sciency' thing that the 'unsophisticated masses' couldn't care for (or shouldn't care for), it's that spaceflight is mundane. Noone is going to watch these people eat MREs and float around all day doing undescribed obscure technical tasks. And if the psychological and interpersonal relationships of the crew are massively played up for drama, there are huge ethical questions to be asked as well. Dealing with those issues during a Mars mission are bad enough, but to have that played for entertainment to millions back home? That too sounds like a form of brutal entertainment.
But no worries- I'm sure the idea of mundane people doing mundane things would be an absolute reality TV hit. In fact, (wink wink, nudge nudge) I plan to demonstrate it myself- I will launch a rocket from the Overberg Test Range by 2023, and I plan to build it in my backyard, funded by the profits from my new television series proposal, based on the trials and tribulations of launch vehicle development...
...it will be titled Paperwork. :rofl: