I have a biased view on this as I think this is a cycling forum, and to me cycling means being out in the fresh air, on a bike, come rain, wind, shine. Turbo trainers are like spinning sessions, good alternative or supplementary exercise.......but in the end.................not cycling.
i used to be unsure about turbo trainer miles, but having recently bought one I definitely agree they should be added! a turbo is in no way 'easier' than cycling! People upload walking, running, working out, why not turbo? this is bike radar training, not bike radar cycling outside! and turbo trainers make up a large portion of peoples training regimes.
Looks like I've opened a can of worms here. I only use the turbo when I have to, I much prefer to be in the fresh air. Due to a medical condition there are times when cycling on the road is unsafe for me so, I use the turbo so I can still cycle in a controlled environment. The alternative? Sit on my backside and do nothing.