I think there is a reason for that.
1.) Zombies and Skeletons don't differ too significantly from specie to specie. There is little difference mechanically between a human zombie and an orc, or a halfling skeleton and a gnome. The MM has a few odd examples, but really the only difference between most is size and HD, and both of those can be done just by modifiying them with the DMG and recalculating the CR.
2.) Celestial and Fiendish only existed for summons; did anyone really ever use them outside of Summon Monster spells? No loss.
3.) Half-fiend template was eaten by the Cambion and/or Tiefling; Half-celestial doesn't seem too important.
4.) Lycanthropes, Vampires, Ghosts and Liches are are just more complex examples of zombies and skeletons; there is little difference in a human ghost and an elven one, and making them complex templates that forced you to build an NPC then rebuild him to add the template was pointless. Again, I'd rather add some HD (to toughen them) or slap on a few racial traits (if needed) or spells to make them unique, no need to make every werewolf or vampire a special snowflake.
So what does that leave? Half-dragon (while dragonborn could fill the niche for PCs, I can see them for monsters), and a few others. To be honest, I don't even think we need THOSE templates either, but YMMV.
I agree on
zombies and
skeletons, if they are simply animated corpses then it makes sense that these don't keep any abilities they had in life. When they do, it's typically because they are other, more complicated sorts of undead. I am not sure about
ghosts, certainly the
physical differences of the original creature wouldn't matter much, but the mental characteristics?
I am also ok without generic
half-fiend/
half-celestial, but I will miss the generic
fiendish/
celestial. Note that I say they are both
generic, and that's why IMHO we didn't need to have both of them, but having one (the latter, which is meant more for animals and monsters rather than intelligent creatures) would be useful. For intelligent creatures, I prefer ad-hoc creations rather than generic templates.
The generic fiendish template (more useful than celestial) is not particularly urgent but I think it would have been useful. Without summons as you say, its main use is in planar campaigns where you want the PCs to travel to another plane and be threatened by local critters, or in encounters with creatures interloping from their original plane and taking pets with them. For similar reasons,
elemental templates would have been very useful already in the MM.
Lich is tricky... the way I see it, all Liches are different because all spellcasters are different. But again the physical characteristics of the original creature are not so important, so they could be overridden. For NPCs, you can simply achieve these by starting off from a fixed monster and choosing spells a-la-carte. What doesn't sit well with me is the fixed CR and thus overall spellcasting level. I still think a template would be very much needed both for PCs and NPCs created from classes, but the alternative could be a Lich "race" that would replace the original one.
Lycanthropes and
vampires templates are the real needed ones. Both of these are
acquired conditions, so it is actually
very important to have a mechanical tool to represent someone (e.g. a PC) become one of them, on top of whatever the character is... I don't have the MM yet, but I thought there was in fact at least some sidebar to cover these.
