That may be true, but definitely not in my experience. I have included my job historically on emails eg: Software Engineer but never my level. I don't even put that on internal emails because I see it as my business and no one else's. This includes when I worked side by side with sales folks from time to time at a start up. If you didn't feel like working with me if I was a SWE I but you feel like it with a Principal, why would I want to work with you?

People do care that someone will show up and answer all their questions in a thorough and non-elitist (read: talking over people's heads) way.

I think your experience is fairly characteristic of software developers. However, there's a lot of other segments out there where title comes into play a lot heavier; where it caries weight in the same way experience does.

It's probably also worth noting that title can impact pay when it comes to a job; a lot of companies have pay caps based on title.

Really, my point was that title is more than just self-gratification.