I think there's a variation in philosophy regarding the emails here.
You seem to be viewing emails as a quick way to get content from the site(s) you're interested in, so you want as much density as you can have, with full-text questions taking up as much of the page as you can.
Now, I'm clearly not an employee of Stack Exchange, nor am I directly knowledgeable about their decision-making on this sort of thing, but this is my guess. I suspect Stack Exchange views these emails as a quick way to promote content from the site(s) you're interested in. In essence, this email is just a newsfeed of the latest headlines, meant to draw you back onto the site to read the full question, comments, and any answers that have been provided. The content of questions isn't meant to give you everything you need, but rather it's there just because otherwise we'd see a lot of emails that are just a list of questions like "Help me with a SQL issue," "Weird error when I build for x86," etc., and that wouldn't draw much interest.
As Laura said in her comment above, no content was removed from the emails, they were simply redesigned to fit a more modern standard, not to mention to look more like the site.
And remember, in your suggestion to include more content, that they have to worry about many devices, and keeping emails small. It's less and less of an issue as time passes, but content providers still don't want to bloat receiving inboxes with huge emails, nor is it worth anyone's time to make an email newsletter like this responsive to work on all sorts of devices.
Long story short, by doing emails like this, they're inviting click-throughs to the site, and promoting a consistent feel end-to-end. A win-win, for what the newsletters are actually meant to do.