One of the most apparent reasons for dimmer switches not being able to dim all the way is the lack of compatibility between the dimmer and bulb you have used. There are dimmable bulbs and non-dimmable bulbs; if you were to use a non-dimmable bulb with a dimmer switch, it wouldn't work out at all.

Why are my dimmable lights not dimming?

Overlamping a dimmer switch is the most common reason a dimmer switch fails. A dimmer can't control too many lights or it will surpass its maximum wattage. ... If you are having issues with an older dimmer, you may want to replace it or double check the wiring.

What are the signs of a bad dimmer switch?