My only AR is in .300 blkout that I built as a pistol with an 8" barrel. I have a MAS defense pistol buffer tube on it with a moveable grippy spongy thing on it. I actually like it more than most stocks, I haven't noticed a difference in accuracy and it lets you skip the $200 NFA tax stamp for an SBR.
Adjustable stocks have their place. Wearing a t-shirt in the summer is one thing, but put on layers of clothing, some tactical gear (whether you are a weekend tactical warrior, or a LEO-military) and you'll soon find you wish you had an adjustable stock.
Same thing if you want your wife, son or friend to shoot your rifle and they are of a different stature that you. Nothing bothers me more than seeing someone shoot from a contorted position because the stock was too long.
Adjustable stock = options. Non-adjustable stock = no options.