Note: This issue is not the same as the missing Jigsaw Blocks issue, here even if some Structures have Jigsaw Blocks it seems like is not spawning the Villagers correclty.

For some reasons it seems like Jigsaw Blocks are not respecting Villager Spawning, like the Villager spawning looks randomized accross all these Structures, in some Houses you will not find Villagers but later on in that same type of Building but in a different Village you can actually find those Villagers generating correctly.

• • Example:
    You first find a Desert Village with a "Small House #2", in this one a Villager spawned correctly from the Jigsaw Block, later on you visit another Desert Village that also has a "Small House #2" but here in this one it seems like no Villager spawned.

And that's how Jigsaw Blocks are working currently, making it feel more randomized and inconsistent leaving a very negative output of find very low Rates of Villager Population.

Update:

As for the Snapshot 19w14a, the Village generation got changed again, meaning all the current Seeds and Coords I provided won't produce the same Structure Generation like before, so I will provide another Seed with the Location to the Village that leads to this issue happening again.

Desert Village

• • Seed: -2510325218424375834
  • Coords: -1456 ~ -2816
  • Teleport Command: /tp @s -1456 ~ -2816

*Lot of houses empty, with no Villager natural generation*

But to Reproduce this issue you actually need to create a new Default World and locate the very first Village that generates close to your Spawn Point and you there's a high change that you will appreciate this Issue happening, but like I said is randomized there's a small chance the Jigsaw Blocks might work properly in all the Houses, but is very rare to see that happen, in a good amount of Villages that I visited so far the Bed Number never match exactly with the amount of Villagers, so that's why I provided Seeds that Highlight more this Issue, but just to clarify is not a region or Seed specific thing, it takes globally any type of Village, even at Buffet/Super Flat Worlds. Overall affects any naturally generated Village Structure that has one or more Jigsaw Blocks set to spawn a Villager here, I believe that this issue doesn't affect Villager but any type of Entity that is set to be spawned by Jigsaw Blocks such as Iron Golems, Stray Cats, Animals (For Butcher Shops, Shepherd Houses and Animal Pens).

(For Old Testing, above 19w14a Snapshots)

I will provide some Screenshots to describe more this Issue:

For personal testing here's the Seed and Coordinates:

Desert Village

• • Seed: 546108167302606462
  • Coords: -736 ~ -880
  • Teleport Command: /tp @s -736 ~ -880

In this Seed, you will encounter with a Village that is set to spawn 9 Villagers, in the Structure Files all these Medium and Small Houses are saved with the Jigsaw Blocks that are set to spawn Desert Villagers.

First one is a Small House, no Villager here:

In the Structure, there's a Jigsaw Block with a Villager set to be spawned tho

Another one without a Villager

Jigsaw Block with a Villager spawning here

2 more with 0 Villagers

Even those 2 have their respective Jigsaw Blocks

The Result was that in a Village with 9 Structures that were supposed to generate with 9 Villagers, only 5 Spawned, the rest failed.

To confirm more this issue I even tried on a different Seed

For personal testing here's the Seed and Coordinates:

Plains Village

• • Seed: -7583095904270334896
  • Coords: -832 ~ 144
  • Teleport Command: /tp @s -832 ~ 144

No Villagers sleeping here means no one spawned in this Structure:

(Even at Peaceful Mode, meaning no Zombies killed a Villager)