There's various reasons. Why would you assume it's related to the file type? Even if Blender couldn't export the .x file type, PMXeditor can import .obj files.
While I assume there are ways to do all the things I use Meta for in Blender (I only assume this as it's a more powerful program than Meta), I find different software more suitable for different things based on my personal preferences. Another example is Adobe Photoshop - just because it can be used for drawing, that doesn't mean I will use it to draw; I'd rather use PaintToolSAI for that. PMXeditor can create shapes, but I don't know anyone that uses it to create models from scratch.
Maybe I didn't make myself clear at the start that this was my process, not "the right way to do things". If you find these things easier to do in Blender, then by all means do them your way! I don't want to be telling people they have to do things the same as me, I just want to show people how I do it and maybe help them figure it out themselves, help them find their own ways of doing things.
Ok, ok, that's find, I didn't read the full tutorial, I just thought that was weird to do a step trough Meta for this particular case, neither Meta or Blender are perfect programs, maybe for other cases Meta has some useful functions that Blender hasn't.
And yeah I discovered recently that you can add shapes and vertexes in the latest PMX editor, and was like: LOL Is really possible to do a model from scratch in PMX Editor? I think that nobody uses that too, Japanese tend to use Meta for that.
I wonder if anyone even has the patience for it? XD
But yeah, that's what I think when it's for PMX models. If I stopped using MMD entirely, I wouldn't even bother with Meta or PMXeditor. I've wanted to convert to Blender, but I also don't want to abandon the MMD community and my MMD friends. I like joining in with what they are doing and I enjoy seeing pictures and comics they've done with my edited models. The MMDC is actually the first 'community' I actually became a part of and felt welcome in. Others seemed to push me out a bit or generally ignored me. People can complain about the MMDC but I've made pretty much all of my online friends from being in it.
I've seen Blender renders and animations, they're so damn amazing, I would never have thought a FREE program could do anything like that. I find it bizarre that more people would rather use Meta to create models than Blender. Personally, Meta seems a lot more 'rigid' than Blender (which for me is only useful for preparing a model for PMXe/MMD), and having to buy a license for it seems almost like a waste of money when something like Blender is available, just compare their abilities! There are some 3D animation courses that actually use Blender, it's certainly recognised as a suitable program. Although when I first used it, the controls confused me; like the redo action being CTRL+SHIFT+Z rather than CTRL+Y and merging being CTRL+M (I'm used to thinking of it as 'join' because it's CTRL+J in PMXe and Meta). But once you learn them, it's easy.
You can apparently do some UV mapping in PMXe too, but I'd rather use Blender for that because from my experience, it seems to unwrap meshes really nicely and of course, it's free! (But admittedly, I don't have that much experience in it, I'm often too lazy or impatient to bother with mapping unless I think it's important for the design but if I ever wanted/needed to, Blender's my first choice.) There's a Meta plugin that makes it easier to do UV mapping than the default method Meta offers, but I still don't think it works as nicely as Blender's unwrap tool.
Overall, I think MMD is a good starting point for people interested in 3D art and a nice thing to do with friends; especially if you don't have a powerful PC, but Blender seems to be a lot better at doing the things that MMD/PMXe/Meta do combined - I just haven't learnt all of it yet. (And being able to have smoother meshes... I always disliked the way MMD models have to be low-poly. You can usually tell something on a MMD model is mine because it will usually have way more vertices than it should. I try to keep it at a minimum, but I just love nice, smooth meshes!)
My brother always bothers me saying that I "extend to much" when I write something (In Spain we would say "te enrollas mucho"). But you sir write much longer comments than me xD.
Well I'm not saying that you should pass to Blender and forget the MMDC, it's the opposite, use Blender capabilities to help the MMDC. For example, I'm doing my first model edit in Blender, after some practice I could even make my own base and share it to the community (In fact I already tried to do that, but I failed XD, and then noticed that maybe it was too early for that), I had tested already 2 different PMD/PMX import-export scripts of the 3 that I actually have, I'm doing that just to find which one should be the best to use for the MMDC. Also I have planned to develop another MMD, Open Source and multi-platform (So Linux and Mac users could use it too).
I think that proves enough my love to the MMDC, Blender is a really good 3D Authoring Tool (calling it 3D editor is just not enough, it even has a built-in game engine), but I think that the interface is too much overloaded for the newbie user, and it's not focused on Animation, so it has so many options that someone that only wants to animate don't need, that's the main advantage that has MMD over Blender. With MMD someone that don't have any idea of 3D can create an animation easily by combining models, stages and motions that are already there in the Community (something that don't happens in Blender), I want to support that collaborative work-flow that I love so much