SmartThings support says that hue bulbs can only be used if they are connected to the hue bridge. That’s because if you do connect it directly to the SmartThings hub, you will not be able to reset the bulb again without purchasing an additional device.
That said, there are people in the community who are using Hue bulbs connected directly, and there is a community created device type that you can use.
If you don’t yet know how to use custom code, here’s the FAQ for that:
Again, though, once you have directly connected a hue bulb to the smart things hub, you will not be able to use it with a Hue bridge unless you do a factory reset first, and that requires an additional device.
Most other brands use a “blink method” for factory reset where you just turn the bulb on and off in a specific pattern and it resets itself. Phillips chose not to do that out of concern that a child playing with the switch might inadvertently reset the bulb. But it makes it more complicated if you try to use their bulbs without a bridge.