Serena is 5'10" tall.
Fed and Sampras closer to 6'1".
With that 3" of extra height, the REACH can be well over 6", possibly as much as a foot, for increase leverage.
For example, I'm 5'11", or a 1/4" shy now that I'm 64. My contractor is 6'1" tall. His standing reach, flat footed, is well over 9" higher than mine. He reache's over 8'2", while I only reach 7'4".
Another thing, feetsize. Big feet can help raise your body for higher contact point, leading to better and higher percentage of getting serves, especially fast ones, IN.
I'd guess Serena has big feet for a woman, but Fed and Sampras had shoesize 11.5, which is like size 13 in women's sizing.