There's no objective reason. Just for practicality and old skoolness I suppose. I like collecting cars and tracks but dynamic TOD/weather aren't really high on my priority list of things to have in AC. They are nice and I love the ingenuity of modders who can make it happen, but personally the file modifications needed to put it in the game is a bit too involving for me. It feels like there's not a clear one stop shop to download every file you need, and not a clear step by step instruction to do it so I'm wary of breaking the game. Also not all mods (especially old ones) support the full functionality so it's always hit and miss.
My laptop is mid tier from 2014 so I run conservative graphics settings anyway. As long as I can hit 60 FPS on 1080p I'm happy. Not too bothered about 3D mirrors as well since I mostly time trial.
As I've said many times in this forum, I still manually unzip and copy paste every single mod I have (600 cars and 100+ tracks so far). I also have a notepad file with every mod name, source and version/date. I only use CM because the standard AC launcher couldn't handle the number of mods I have anymore

So I'm very paranoid about anything that changes the basic file structure of the game, and because of that I probably won't ever use the custom shader/Sol mod unless it becomes a sort of standalone launcher like the Power&Glory mod for GTR2.
I found my twin in thoughts... except the labtop but It's not a thought ! ^^
I agree all you said, thanks a lot for translate in a perfect english what I'm not able to write and comment correctly.
Cheers !
@kondor999
Pleeeeeeeeeeeaaaaaaaaaaaaaaaase, I think you are boring most of the gentle people here with the realism police. ;-)
Realism in virtual !?
So much to say !
Is it forbidden for some casual gamers (I'm not a part of by the way) to have some fun, even if You are thinking It's unrealistic in "true life" ?
I got some strong capacities for telling you !
I won numerous championships on 2 or 4 wheels (and other weird machines), I'm so much better in awards than Michel Vaillant.
The better I did was in "Grand-Prix Legends", I won the 1967 drivers championship at the age of...3 !
Yeah but... in "real/true life", I will not able to be fast as John Surtees on Monza with the Honda RA300, I will not able to drive a Porsche 917K, I will not able to simply start correctly, in 1st gear, a Lotus 98T in a pit to after, piss on me, by fear of the tremendous acceleration ! ^^
So, what is really "real" in a simulation !?
I can't make a count of the times I died in a racing car... virtually !
I can't imagine push hard the throtlle in a "rolling grave" full of fuel on the "Old" Nurburgring in reality..!
We are just living some "real" dreams in virtual and that's simply fantastic ! ;-)