Well, its just that road bikes are made for the road. And if you are spending alot of money on a road bike (which is a relative thing anyways depending on what your budget is for a bike) then why on earth would you clamp the forks into one place and then apply pressure in your indoor ride that the frame would not usually have on the road.
On the road, as you lean from side to side, the bike leans with you, the handlebars move, it responds to your requests.
On a trainer, your bike is fixed upright, it cannot move with your movements. And this is probably ok if what you mostly do on your trainer is sit and spin. But I stand, I practice timetrialling, I get tired and start to pulll on the handlebars and I don't want to put my bike through that.
A complicating factor in our house was the number of us wanting to use the indoor trainer... so we were constantly taking different bikes on and off the trainer... and IMHO, your shouldn't mess around with taking your bike apart - even if its just the front wheel - any more than you have to.

