I personally tend to use "common assets' far more than any template. Common assets meaning, swatches, paragraph, character, object, table, graphic, layer styles, brushes, shapes ... An InDesign library containing commonly used artwork (bursts, banners, buttons, etc). Those sort of things.
I only use what could be called "templates" in a couple areas....
For InDesign... a blank document set to the size I need and containing general Paragraphs, Character, Table, Cell, and Object Styles I customarily start with. But I always then alter for each piece. I don't have any "templated" layout which contain any actual artwork though (save maybe page numbers).
For Illustrator/Photoshop.. I have nothing... except maybe stored color swatches, brushes, styles, etc. But those are more common resource files than "templates".
I do tend to not use Photoshop/Illustrator for layout purposes. If I were to use them to that extent, I'd have the same basic document setups I do for InDesign. Just blank pages set up to size and containing general styles for use - no preexisting art though.
For web pages/emails, yes I have templates. Various HTML/CSS pages with layouts for different uses. This is probably the only area where I have set up specific elements with colors, type, sizes, position etc. And then adjust as a project requires. Web page templates are far more about saving time and effort by not requiring me to rewrite markup than about design choices.
(I don't really do UI design.. but if I did, I'd treat it a lot like web design... and I'd have UI templates with formatted art for buttons, etc).
For me existing artwork templates are a road block. They set my creative thinking down a specific path. I then must force myself to veer off that path consciously. By starting with a blank slate, I force myself to be more creative rather than forcing myself just the be "different" than the last time.
I do tend to sketch on a small, crappy, wire-bound, notepad I keep on my desk. It's just faster to scribble by hand than to use applications for exploring ideas. (Except web design.. wireframes are faster.)