Sometimes soldiers are very slow in putting on all of their gear. Picking up equipment seems to have a very low priority, so if they have a barracks they can train at they may go on duty and train in their barracks while wearing only a single boot, with the rest of the shiny masterwork steel plate just sitting around in bins while the recruits get brained from training spears.
Something must've changed in 0.34, then, since whenever I enlisted soldiers in 0.31.25 they'd immediately put on all of their equipment before reporting to the barracks. Granted, they were also completely naked at the time, so there weren't any issues with clothing getting in the way (never had to set them to "replace clothing" instead of "over clothing", which seems to be an extremely common problem in 0.34.11).
I did notice in earlier versions they grabbed gear much more aggressively. In my current 34.11 games my soldiers seem a bit lazier about the gear.
I'll set up the barracks first, then assign a bunch of soldiers to the squad, assign the squad a uniform, and set the squad on duty. They used to rush off to the stockpiles and suit up right away. Now they still do that, but they only seem to grab 2-3 pieces of armor, then head off to the barracks and do their training thing. It takes them a very long time, sometimes as much as a year, to get fully equipped. Between training sessions they might grab 1-2 additional pieces of gear, or maybe nothing at all.
If I set them to active but give them no barracks, they suit up fully right away all the time, then idle in soldier mode in my meeting zone.
My guess is that picking up new equipment seems to be a lower priority job now, and a barracks is constantly giving them higher priority training, combat drill, or sparring jobs.