While it is true that being on the NomCom does not require deep policy expertise, it does require a good familiarity with ICANN's different constituencies, their relationships and indeed the politics between them. You need to be aware of everything ICANN does -- or at least needs to do -- so that you can sufficiently choose people for its Board. You also need to know about the committees -- besides ALAC -- to which the NomCom chooses delegates.
Furthermore, as Marita said, being on the NomCom separates you from the rest of the community. You may travel to ICANN meetings but won't be spending much time with At-Large colleagues. Your meetings will be intense, with the same small group, and you will be sworn to secrecy so that you really can't even tell anyone what you're accomplishing. Meanwhile, you'll be doing fairly little relationship-building beyond the NomCom even if staying at the same venue as everyone else.
And finally, I take issue with the assertion that "people interested in leadership roles may not be selected if they're not familiar to the decision-makers". In NARALO the "decision makers" are your peers -- the other members and ALS reps that make up this community. It is they who choose committee chairs, vote for NARALO leaders, and select two of the three North America members of ALAC. Showing interest alone does not demonstrate commitment, it is not enough just to show up. You need to do things -- speaking, writing, meeting, convincing, and above all learning. Earn your colleagues' respect and trust first, and then go for their vote.
Cheers,
Evan