As Ian pointed out in another posting, and you say here, Python has all the bits. What it lacks is the "quickstart" appeal. Whatever you call it, that's what's missing. And I don't see this as "playing catchup to Rails" - it's a simple case of providing entry-level, tutorial type documentation and sample material (something that open source projects are notoriously lacking in, because none of us like writing it).
I don't think there's any need to evangelise a "one true system" for object publishing, or for templating, or whatever. Each has its strengths and weaknesses. But picking one set (and accepting the compromises) and doing a really good job of putting that quickstart tutorial together will add something extra to the mix. Subway sounds interesting, but a first glance makes it look like (more) packaging and "layers". I'm happy with a toolkit of "bits". I don't really want a packaged solution, I want a first step up.
Heck, I'm very close to going it alone, and building something for myself. I found a document the other day called "Four Days on Rails", which went the step past the 10-minute demo video, and showed how to start customising the initial application. I'm seriously considering doing something similar for Python, starting from SQLObject, Cheetah, and Quixote (or maybe CherryPy). But my graphic design skills are dire. I'm going to find it very hard to write something along the lines of "look - it's easy to build a basic web application in Python" when I can't even stomach the look of the result myself :-)
I don't know if I'll ever get round to doing this (my life is a mess of part-completed projects...) but I'm not sure that waiting and hoping someone else will do it for me is going to work, either.
(And I even looked at Rails, but I can't get my head round Ruby so I'm probably safe from the temptation to swap languages for a while yet...)