Good maps not published on the workshop
Currently, the workshop is flooded with maps that are a bit easy and not to much time has been put in them. (Otherwise known as maps that would get 1- ratings on this website). But, before PTI came out, maps were so much better, and now, most of them are not published on the workshop. I thought this would be important for a change in maps on the workshop.
PortalStories.com
"Oh, in case you got covered in that repulsion gel, here's some advice the lab boys gave me: DO NOT get covered in the repulsion gel."
Yishbarr if you are worried about the authors of the maps not posting to the workshop, PM them and tell them why they should put their map on the workshop. It is literally 2 entities and an output to get potential 1000s more plays.
I don't think that good maps are not being published in the workshop (do you know a good example btw?), but they are much harder to find. Overall because most of the top rated maps aren't good at all, so where will you start searching for the best maps?
A thread about this (difficult to find but good maps afterall) were created here.
useful tools and stuff here on TWP 
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Patent Pending Infinifling and Edifice were all good maps from the first mapping contest that aren't on the workshop
Yeah, but even the maps that didn't have too much detailing were good maps. It's just amazing how PTI ruined it all.
Keep in mind that there was no workshop before PTI, so it's hard to say that PTI ruined it all.
And while I agree that there's a lot of bad maps on the workshop, there's also a lot of good ones that probably would've never come to existence if it weren't for PTI. And there's a lot of good mappers who wouldn't be as well known if it weren't for their PTI maps (see: Mevious). I personally think that the PTI was a good thing for mapping because it's led to some new people getting into mapping, as well as causing absolute gems of maps being made. That said, the Workshop would benefit from having some top-tier maps like Edifice and Patent Pending on it.
Patent Pending Infinifling and Edifice were all good maps from the first mapping contest that aren't on the workshop
Yeah, awesome maps! 
But those were pre-PTI (thus pre-Workshop) maps... Maybe the authors simply didn't want to upload them to the workshop after it begun to exist. Talking of Omnicoder, Restrospective isn't in the workshop either... I was referring more to maps from the dlc2 onwards that haven't been published to the workshop`...
I agree with srs bsnss here. Even though there are tons of crappy maps, there are REAL JEWELS out there, awesome puzzle makers (although not mappers), that we all must thank the PTI their appearance.
useful tools and stuff here on TWP [spoiler]
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Sadly Retrospective doesn't work anymore, and couldn't work on the Workshop. It used the Addon system which VALVe ruined in DLC1. One would have to make a new DLC for it.