Orchestral stringed instruments are bowed most all the time, not plucked. The sustain when plucked
(pizzicato) is minimal. Their bridges are optimized for sonic transfer and response when bowed. The cutouts in their bridges aren't to save weight, they influence how the vibrations reach the soundboard.
Plectrum or fingerstyle played arch top or floating bridge instruments (mandolin, mandola, octave mandolin, mandocello, banjo, guitar, etc.) bridges are optimized for sonic transfer and response when being picked or strummed. Also, the height of the bridge above the soundboard on one of these instruments is way less than on a violin, viola, cello, etc. Similar action on an archtop guitar from a bridge like that would make it unplayable.
That said there are bridge makers (
Red Henry for one) that make one-piece bridges for mandolin with cutouts similar to a violin. I've stumbled across similar concepts for archtop guitar. I have never tried one myself. On most gypsy jazz guitars the floating ebony bridge is a one-piece design with the saddle portion partly hollowed out. These guitars are quite loud and not typically known for sustain.