Someone must have a PE to sign off on certain things when dealing with regulators and so forth. Which makes getting a PE in certain situations important. But not having a PE is hardly equivalent to calling yourself a lawyer if you haven't passed the bar in a state.
http://www.mystatesman.com/news/state--regional-govt--politi...
And the relevant court case:
http://www.soah.texas.gov/pfdsearch/pfds/460/16/460-16-0550-...
-> 1 - 30 of 3,061 positions
doesn't seem to have scared too many away from the title..
I'd note that's a case where a business is representing themselves as an engineering firm and, and in some situations, it would be reasonable to expect that meant they employed licensed engineers. (The specific case is pretty silly though so is calling themselves engineers.) But individuals certainly call themselves and are called engineers all the time who aren't licensed in Texas and everyplace else.
Edit: Thanks for the answers. 2 questions:
1. Why would you not do this?
2. Were you to do this, what precautions would you take?