There are competitive states and competitive districts w/in states. States that typically are competitive (for USNA at least) are MD, VA, PA, TX, CA, FL and probably a handful of others. However, there can be districts w/in those states that are not very competitive. Likewise, there can be competitive districts w/in non-competitive states. That often happens in districts that include a large military base.
In competitive areas, MOCs will often force you to choose one SA or to rank your choices -- with the intent of giving you only one nom max. That can make it impossible to get noms to more than one SA.
In other areas, there are more noms than competitive candidates and therefore the MOCs may give you more than one nom.