It takes away a couple steps that add cognitive load (aligning sights, focusing on front post), so you can focus on your core handling mechanics better. Additionally the sight window enables you to see a large portion of the target whereas with irons you only see the top half, so it's fundamentally more natural for how human vision targeting works. The reduced cognitive load allows you to focus on making the right shot and allows you to focus on your target instead of the sight.
They're better in every conceivable way except for concealing and the very rare time you run out of battery or break it. The model I use, the Sig Romeo 1 has a 30,000 hour battery time and turns itself off when you're not using it, effectively giving it years of use time. And many sights are set up with a co-witness BUIS in case of failure, however most defensive shootings occur within 15 ft where you're likely shooting completely on instinct.
I imagine within the next 5-10 years you will see widespread police force adoption. The ability to acquire your target without taking focus off the subject allows an officer to "keep their head in the game" with better situational awareness, which can save lives on both ends of the barrel.
There's no reason to not have a red dot on your pistol aside from price point.