IoT enabled light bulbs have been on the market for a while now. The Philips Hue is probably the best known. But I think controlling bulbs directly is a rule-maintenance disaster waiting to happen. If a bulb goes out (and yes, LED bulbs do fail), you have to replace the bulb, and remember to update any scenes or other rules that control the bulb (or are triggered by the bulb.) Or if you move a bulb from fixture A in the kitchen to fixture B in the bedroom, (perhaps while cleaning), the rule that says "Turn on kitchen lights" will now illuminate the bedroom.
That may not seem like a big problem today for those of us who understand the configurations of our home automation systems intimately, but imagine a home automation system set up by a professional integrator for a typical customer. The homeowner may not know how to change the rules, so replacing a lightbulb could cost them not only the price of the smart bulb, but an additional service call charge from the integration company. A smart switch or fixture solves this problem because the switch doesn't move with typical maintenance. (The switch offers the same problem of configuration if it fails and needs to be replaced, of course, but switches typically have better life expectancies than bulbs, which are generally considered consumables.)
On the other hand, an IoT enabled light switch can't fully control every aspect of lighting the same way a smart light bulb can. A switch can do simple dimming for certain technologies of bulbs, but it can't control the color of the Hue bulb.
Much worse, smart switches use different types of electronic circuitry to perform dimming, and must be carefully matched to the technology of the bulbs they are controlling. A typical older dimmer can dim only incandescent bulbs and not CFL or LED bulbs; some dimmers can dim both incandescent and CFL but not LED bulbs; some dimmers can control incandescent bulbs and LED bulbs, but not CFLs; and some dimmers can control inductive loads like halogen transformers, but not CFLs or LEDs! With incandescent bulbs being replaced because they're such energy wasters, this has been a real problem, too.
So what's the most practical approach? Buy expensive bulbs that are directly controllable and expensive smart switches to control them, or buy cheap bulbs and just expensive smart switches, and give up on the idea of controllable color lighting?