Yes. These people may already have made a commitment to others. If so, they will not have enough resources or time to make a further commitment (e.g. to you).

I am more used to "being committed to something"

As far as I know, there are no meaningful differences between the two expressions. "Commit to" is at the infinitive form of the verb and can be conjugate depending of the subject of the sentence. "Comitted to" is in the passive voice, and the verb is being used in the past participe. It means that the thing has aready suffered the action expressed.