One of the benefits of the metric system -- versus the imperial system -- is that you have fewer conversions. Rather than having inches, feet, miles, furlongs, rods, hectares, acres, gallons, fluid ounces, teaspoons, and so forth you have meters. Then you can have centimeters, kilometers, square meters, cubic centimeters etc., but you can convert amongst them trivially.
The temperature scale didn't have that issue. These days, the main advantage of the Celsius scale is its near universal ubiquity (which is a significant advantage, by the way!).