To put it bluntly.
The only reason not to have all as en suites is if there's ever going to be a situation were someone doesn't want to take a shit in their bedroom.
THIS
Mumsnet teaches us that, even if you've been married to (and presumably very intimate with) somebody for 40 years, it is still a disgusting and unthinkable thought that they might discover that you sometimes do a poo, as it isn't always possible for a married couple to spend every night at least one county apart.
Having an en-suite completely gives the game away and betrays your filthy little secret to them. Your marriage may not survive this and it would all be 100% the fault of the en-suite.
The only way it might work would be for everybody to use an en-suite per bedroom - but not the one attached to their own bedroom.
"Good morning my little Room 1 primrose, how are you this fine day?"
"Why, sparkling, thank you, my Room 1 dear. Do excuse me, I wish to go and enquire of our good friends in Room 4."
"Why, hullo! It's one of our two trusty companions from Room 3 come to extend her warm felicitations to us!"
"Glad tidings, Room 2! I do apologise for your discomfit, but Room 5 has requested the company of your good gentleman occupant on this, the beginning of another fine Spring morn!"
It would be like one big platonic wife-swap, with everybody desperate to avoid pooing in the earshot of their spouse!
Oh, and for those expressing horror at the thought of 'pooing in the corner of your bedroom', you do realise there's traditionally a door and walls surrounding an en-suite, don't you? The same kind of door and walls separating ALL of the rooms of the house, including the family bathroom?
If that shocks you, then you'll be mortified when you eventually discover that everybody you see in the High Street is absolutely, totally, completely butt naked underneath their clothes....