dont forget that challenge is just challenge, is just a shot, if u have some doubt. One single overrule by challenge is a big succes. other way u would lost that point...
Of course, you are right, but also bad challenge leaves you with less chances for the controversial points later in the match.
However the only one I saw wasting all her challenges early was probably only Kuznetsova vs Radwanska in 1st set. What was that? 3 bad challenges at 1-3 in first set
I didn't see that in ATP, they seem to leave the challenges for the latest parts of the set, which is quite correct from the tactical point of view.