Now I will admit, wooden kits for war gaming and modelling uses have been around for a while, but it's only been in the last few years that anyone's really taken notice, particularly 40k players, whose terrain needs have been, in the past, somewhat sated by GW's plastic kits. So what makes wood better than plastic?
Cost
Nine times out of ten, it seems that wooden laser cut kits are far, far cheaper than GW and equivalent kits. Take for instance the above large building kit from TT Combat, in 28mm scale. It cost me less than £9 (with discount). The equivalent to this from GW is the Sanctum Imperialis at a whopping £20. Another example is the ruined sector, from GW it is £70. A similar kit, again from TT Combat, which includes two full ruined buildings (each in 4 parts, so up to 8 tiny buildings or a fair mix), 2 shipping containers, 3 walls and 5 barriers, is only £18.
Details
There was a time when wooden terrain was pretty basic stuff. With advances in computer programming and more time to develop skills, some kits that are being made today feature a surprising amount of detail, with some even featuring intricate textured surfaces and layered surfaces.
Ease of assembly
For the most part these kits are easy to assemble, and in most cases can be built without any glue (though from experience I still prefer it). Whether you have PVA or nothing at all, you can enjoy easy to build pieces without the toxic fumes that poly cement and super glue gives off. Even though PVA isn't an amazingly strong glue (you can use wood glue), the way these sets go together means they will be strong enough anyway without risk of collapsing. Still, I wouldn't stand that depleted uranium Chaos Dreadnought on the top floor anytime soon.
100% Recyclable
Mother nature is taken care of here (don't worry, this won't turn into a Green Party conference). Being made of wood, it is completely recyclable, and as far as I can tell there isn't any special coating or toxic treatment. This is a nice little bonus when it comes to the time to get rid of the terrain (as much as I love MDF terrain, I doubt it has the same longevity of plastic). I've often struggled to work out if plastic from GW is recyclable, with wood it's. Also, if you're cool/a hipster/camping and you need some firewood, the sprues have a second use.
They now make actual models from wood!
The general market is flooded with terrain pieces, but occasionally you can find usable MDF models. The above is a near-perfect stand-in for a Necron Sentry Pylon, and at only £7 it is seven times cheaper than the Forge World kit, and would even undercut the worst painted Ebay listing. Obviously it doesn't have the same level of detail, but if you're on a budget (many of us are), then this is an amazing saving.
Sure there are a few downsides; they are a bit more fragile, the joins and connections are far more obvious, and if left untreated for too long, very vulnerable to water, for those who need to count the pennies, and those who want a pleasant, easy kit to assemble to pass some time, look no further.