Guys, no reason to debate this. The simple reason is; DMs don't like Necromancy in the hands of PCs. It creates huge numbers of bodies that insulate the PC against plot developments. You can't threaten a wizard that can just use a few of his class features and a loophole in a spell to turn a Death Tyrant into a subservient slave for an entire month and then just sick his floating skull of death lasers onto an unsuspecting dragon. You can't threaten a master Necromancer with a zombie plague when he can just say "No, you're going to put Terry the Tiefling down and do MY bidding now." And above all else, it's just a tremendous pain having to keep track of an army of zombies, whether the player or the DM is doing it, it's just a pain. So, most DMs don't bother broadcasting graveyards because they either A. hold no relevance to the story, or B. are trying to disencentive the party Necromancer from looking for an army to sack the town.
What? You are missing out. Having a Necromancer just SCREAMS out plot devices:
1. All the commoners get freaked out so refuse to deal with the PC's.
2. Relatives of the dead look poorly upon such things, including Uncle Wizard, Aunt Paladin, and their old friend Mr. Arch Cleric.
3. The local real necromancer gets upset because PC are stealing his stock and business.
4. The rest of the non-human undeads tribe just cant believe the PC cheated their tribe mates out of their honored dead status and seek to rectify same.
5. The stench of the undead ensures the PC can never surprise any creatures, especially those with scent as a trait.
6. Better get used to sleeping outside as no establishment wants your minions in there.
7. The PC Necromancer and PC Paladin cant possibly get along unless one of the converts alignment to others.
8. Evil non-necromancers certainly want the PC undead minions for themselves so will constantly harass the PCs.
9. The Necromancer cabal wants to know any secrets the PC necromancer has, so will of course constantly send their minions to capture the PC's
10. Any undead uprising or horde is met with Good Churches strike teams with the Right of Annulment, authorizing them to eliminate the threat by any means necessary.
10a. If the first strike team doesn't succeed then the situation escalates with better strike teams until Aculard or Constantine show up.