You're right, but doing that is usually discouraged for two reasons:
1) It gives people warm fuzzies to see the padlock icon on any page in which they are entering private information. In that case, they do not see the padlock on that page. If the submit button has a non-encrypted page as its target, you will get a pop-up warning you.
2) And because of this, the default configuration with IE is that the browser pops up a "You are about to send information over a secure connection" pop-up, which is good, but can be confusing to people.

Most web sites are designed such that people get the fewest pop-up warnings from the browser, to reduce worried help desk calls .