local search terms that do not trigger a map listing in google web search

How are local search google map listings generated within google web search?

internet marketing bristol

yields no map results within the web search (yet there are loads of results if you search in maps)

however a term such as plumbing yields 7 results in the web search alone...

plumbing bristol

Are there only some professions google wants to list in the web search?

Is it best to find a category that nearly matches yet displays map listings for "web" searhc even if its not the best choice?

Thanks!

The Big G stated that there would not be any Local returns for SEO/IM related terms some time ago, I think with the May Day update. So now those queries only result in organic returns.

Yep this happened a bit ago. I use to get local map listings for SEO/WD/etc stuff but then it went bye-bye. There are still random ass terms for the same market that I see bring up map listings. But for the most part they are all gone.

cheers guys - yeah did a bit of checking; not many related terms showing at all