Otherwise every keystroke you made would be sent to Google.
This lets you do queries like such:
Type "g hello" into the url bar - googles "hello"
wa integral from 0 to 1 of ln(x^4)dx - can be set to wolframalpha
w France - my wikipedia one
Edit: judging from the other comments, maybe you have already.
If you don't have a separated search bar, your only options are enabling or disabling autocomplete. There is no option of using autocomplete just when you want it.
Also, the local autocomplete of the address bar is great. Count me as another one that does not want to miss it.
What I like about Firefox (versus Chrome specifically) is that the AwesomeBar gives much better suggestions from your history, doing full-text searches in titles - within Chrome I can rarely find something in my history without opening the history view and seriously, most searches that I do are for things that I've already seen and it saves a lot of roundtrips to Google (hint, hint), plus searching for things you can barely remember on Google, which you end up doing in Chrome, is like searching for the metaphorical needle in a haystack.
Plus, as others said, I like it when the browser cares about my privacy. On Android on the other hand there's only a single bar due to a lack of space, but it asks you if you want to activate Google's search suggestions.
Yes. And bookmarks, for me. Back when I had switched from Firefox to Chrome, I thought it hadn't imported most of my bookmarks. Chrome would hardly ever show me the things I expected/wanted.
Having switched back to Firefox, I'm delighted with the experience of it actually suggesting the things I want, again.
The only time I use Chrome these days, is for something Google can't be arsed to make work correctly in other browsers (e.g. photo editing on G+, label dropdowns in Gmail, ad nauseum).
Right click in the tab area, select "Customize" and then drag it to the available icons panel. Searching works from the address bar too.
It is also probably there still because you can select where you want to search, so you can pull down the menu and search in Twitter, or Amazon, eBay, Google translate, Google maps, The Pirate Bay, Wolfram|Alpha, YouTube, ....
For example, "^ hacker news" will only search your history, and "* hacker news" only in your bookmarks.
You have three somewhat simple options for the search/url thing:
1) Have a single box, do not offer search suggestions. 2) Have a single box, offer search suggestions for the stuff users type in it. 3) Have separate boxes; offer search suggestions for the stuff typed in the search box but not the stuff typed in the url box.
#2 involves sending everything the user types in the url bar to the search suggestion provider to check for suggestions
Firefox does #3, because #2 is not considered acceptable from a user privacy perspective.
There are probably more complicated options here like only offering search suggestions if the string typed so far doesn't look like a URL or something that might protect user privacy better than a straight up #2. But it gets easy to screw it up and leak private user data to the search provider....
How would this work? Lets say I wanted to search for Wikipedia, perhaps because I know there's news about it. How would Firefox know I was going to type "Wikipedia" and not "Wikipedia.com"?
Presumed privacy - Some prefer to not send their direct traffic and history title strings through a google search input.
Usability - search engine autocomplete/suggest can interfere when typing a page title from your history.
Money - traffic volume referred to search engines is significantly increased by merging URL and search inputs.
Edit: wow, parent had zero responses when I started typing this!
The urlbar is already capable of searching though. It just doesn't give you suggestions for the reason above.
Context Search (adds a context menu dropdown when you right click highlighted text; think plaintext words you search in trouble ticket type stuff) https://addons.mozilla.org/en-US/firefox/addon/context-searc...
Add To Search Bar (adds an option to search-engine-ify any submit text box) https://addons.mozilla.org/en-US/firefox/addon/add-to-search... (might as well mention https://addons.mozilla.org/en-US/firefox/addon/organize-sear...)
Bonus productivity favorite: https://addons.mozilla.org/en-US/firefox/addon/tree-style-ta...
So yeah, you'll pry Firefox away from my cold dead hands.