Do you all really think a tennis ball flying between 150 and 210 kmph can hit the net and dye just behind ?
If yes I hope you are not working as a calculator in military or industry !
Only a magician like Fabrice Santoro should be able to serve such a ball serve and he would deserve the point.
Big returner like Kolya or Nole can argue saying that affects the way of the ball but net can also makes the ball seed really slower and help returners on other points.
By the way in volley ball small serves is a tactic paying off (because at the top level with the latest rule of "libero" the worst receivers and better spikers are in the front line). Those dying serves are side effects of those small serves.
In tennis I never saw an actual small serve except maybe Chang Lendl in The French final.
Obviously you didn't watch the Challenger of Dallas because it happened on at least 3 occasions on center court matches that I called.