The first tennis serve is weackest earliest
Very likely the typical club player’s serve isn’t much of a weapon under the best of circumstances. It’s even less threatening when a player isn’t warmed up, isn’t into the match, isn’t relaxed, and isn’t really comfortable with their serve, which exactly describes the conditions for your opponent serving first in the match. It’s amazing anybody ever wins their first serve to open the match.
At the pro level, there’s a very careful approach to the serve. You’ll see in their warm-up just prior to the match that the serve may get the most attention of all. In most cases, it must be working and working well to win, so they make sure it gets lots of attention before play starts. Even then a pro isn’t serving at his or her strongest early in the match and, obviously, neither are you or your opponent. A mediocre serve that can’t overcome all the early handicaps becomes useless, even a liability.