Well, had to break my lurking (first post!) to reply to this. I've noticed some oddities in past forts, but I think the masses of novice farmers (including cheesemakers and such) and rangers and fishermen is something most forts have to deal with. However, in my current fort, the first in it's world (started in 34.10 I think), I've had crazy amounts of military-trained dwarves.
I started with my usual (1 axedwarf, 1 marksdwarf). First time I started out my new starting gear of 6 picks (7th guy is the woodcutter) but no mining skill for anyone - it levels up pretty fast. I now have 177 dwarves, of which 48 are babies&children = 129 adults, of which only 30 *didn't* arrive with something like speardwarf 3/shield user 1/dodger 1.
More precise figures of the adults who have survived (I've lost a few dwarves, only 2 in military service though):
1st wave: 6 alive now, 1 without military skills (I'll call them "civilians" from now on)
2nd wave: 8 alive, no civilians
3rd wave: 25 alive, 5 civilians
4th wave: 9 alive, 1 civilian
5th wave: 10 alive, 5 civilians
6th wave: all kids (DT quirkyness in tracking which wave babies belong to, I guess?)
7th wave: 34 alive, 7 civilians
8th wave: 31 alive*, 7 civilians
*(remember, adults - the 8th wave arrived with 52 dwarves, now are showing up as 63. Just not stopping with popping those babies.)
So, usually 80-100% of adults have had either one melee weapon skill at 3 + shield user, armor user, and dodger 1, or marksdwarf+something. A couple of higher-skill melee dwarves in waves 2-4. 1 wave (#5) only had 50%. Never seen this kind of thing before, although I've only played with DF2011 and later, I think, and not that much even then. Annoyingly, I don't have much use for all the military, since I've yet to see a siege in my 4th year. Only 1 minotaur, 1-2 snatchers and maybe 3-4 kobold thieves, too.**
I was just assuming it was some sort of cultural bias, as in, your civ had some sort of bias to military, maybe another to something else, etc. I've also gotten like 4 dwarves with building designer, I've had several 100+ dwarf forts earlier with no immigrants with that skill, ditto for eg. organizer/record keeper, but now i've gotten immigrants with those.
** What might be a factor for both things, is that I'm living pretty close to some other dwarf sites (not my civ's) in the middle of this medium-sized area completely surrounded by mountains (with all the passes inhabited by dwarves). The info for the embark site did list red ----- goblins, though.