Not everybody, able to use them, likes them - and not everybody, liking them, is able to use them. The reasons behind the decisions to use them - or not use them - are fascinating, when examined in proper context.
The most restrictive reason comes from their most major feature - the blog, when displayed, gets the post content from the blog feed, and is published locally on each client computer.
This excludes two groups of blogs - those published with no feed, or with a partial feed - and those published privately. As noted many times, a private blog will not publish a newsfeed.
Depending upon readership, some blogs may have potential readers who are overly concerned with computer security.
In either case - with a blog not publishing a full newsfeed, or with a computer owner who filters web content too strictly, the would be blog viewer sits there, watching the turning gears, instead of reading the blog.
Besides the technical restrictions of private blogs and unavailable newsfeeds, and of computer security, Blogger has made a strategic decision, and disallowed these templates with "Adult Content" blogs.
In addition to the unavailability for some blogs, there are several major design deficiencies - and some deficiencies may be resolved sooner than others.
Besides the use of the blog feed published on the individual computers, the blog, as displayed, is significantly lighter, because the blog feed contains only text and pictures. Various features, important in many blogs, are omitted or restricted - possibly, by design.
- Imaginative text formatting, and other HTML tweaks, in the posts.
- Embedded scripting, in the posts and the template.
- HTML, scripted, and XML, accessory gadgets, in the various sections of the template.
- The ability to add or reposition various features in the post template.
- The various owner designated sections of the template.
- Lack of ability to display the comment form, consistently, may cause a reduction in reader comments.
- The ability to measure and monitor visitor activity.
- The ability to display a post archive index.
- The ability to use an owner designated Jump Break.
- Use of other recently developed features, such as the Lightbox image display.
For a more obvious demonstration, you may display this blog, in dynamic view. For several of the reasons enumerated above, I'll not make dynamic views the default, for this blog.
The good news is that the dynamic templates are easy to apply, and they are easy to remove - both permanently and temporarily.