Why wouldn't there be search engine for the site in addition to the www search box in every site?

I’m not quite sure what you’re looking for here. The search box is the site specific search engine – even if it is poorly designed at times.

Per-site search engine needs to be created by the people who made that website and they don’t always do so. Whereas the “www” search engine is a product of chrome or whatever browser you’re using so that’ll always be there.

If you want to search a single site using Google, use the “site:” prefix.

For example:

‘site:fluther.com bats’

Search on a site is very very very hard to do well. It is much easier to let google take care of it.

@janbb The one on Fluther is.
@Mariah Yes, ”...they don’t always do so.”, which is my point.
@Call_Me_Jay Thank you.
@johnpowell But Google’s search is based what is clicked the most often, right?

There are millions of websites, internal search is not appropriate or feasible for all of them.

But the site specific search engine would be excluding all sites except it’s own site.

Creating and maintaining the site search is time consuming.

Lots of sites simply use the Google search I linked above on their own pages. Google provides the service for free.

I am having trouble Googling up an example (Googling “Google” is hard!). But you have probably seen the “Search by Google” logo around on the web.

Yes @flo. But building a website is not super simple always, and there are millions of websites made by millions of programmers of all different skill levels. Other websites do not really need a search and it is not a valuable use of the programmer’s time. Expecting all websites to conform to having a site search is kind of ridiculous.