Only if you can't control basking temps with basking light distance or if you need a CHE to supplement nighttime heat and it's getting too warm. I have a dome light with a dimmer built in, so I can dial it in without moving lights around and to compensate for changes in ambient house temps. My house is 8-10° cooler in the winter, and with a mesh top enclosure, I need to fine tune the basking light to hit the 105 I'm looking for at his basking spot
A dimming thermostat would automatically accomplish this, but it's much more expensive
I have a cheap thermostat to control my CHE for night time heat in case the tank temps drop too much at night.
Yeah they are quite helpful if you have a set top and can't adjust the height of the lights and it helps automate adjustments due to changes in ambient temps which is nice. I consider them to be a nice luxury to have rather than a necessity though.