Importance of canonical urls outside of parameters?

[onlinesource]

When viewing a page with parameters like ?p=2&store= I understand the importance of canonical urls. What about basic blog pages or even the homepage, does it matter?

I see paid extensions and services which will add canonical urls to all pages including the homepage, etc. Does this really help?

I mean if my site is coolstuff.tld and my homepage is at coolstuff.tld, do I need to have <link rel="canonical" href="http://www.coolstuff.tld/" /> in the source code? It isn't like there are various variations of the url.

[lucy24]

Short version: You only need a "canonical" if identical or near-identical content can be reached via more than one URL.

[phranque]

each url, with or without parameters, is unique.

you really only need the link rel canonical if you are serving essentially the same content from multiple urls and a technical deficiency or application requirement prevents a canonical redirect.

your comment about parameters in urls is more specific to sorting/filtering-type parameters than parameters in general.

for example using the sortby=price parameter in the query string will probably create a non-canonical url while using something like product_id=1620 probably doesn't.