Men will do this all the time as well — they enter into a no-strings-attached affair with the intention of trying to wear the woman down until she agrees to a committed relationship. There is also the risk of investing trust and love into the relationship later to realize that the two of you are not compatible. Maybe you're the one who wants to take things to the next level and announce your intentions to make this relationship more serious. When you are having fun with more than one person, you may be less likely to build an emotional connection that can take things into more serious territory.
Do you get butterflies at the idea of being this person's one and only, or does the idea terrify you and have you running for the door? For instance, a divorcee who is getting back into the dating game is advised to keep things light for a while, so as not to try to avoid dealing with hurt feelings by jumping into another serious commitment right away. Ultimately, the goal is to respect your partner's feelings.