When I worked priviate transport in Philadelphia (2003-2005), I worked for the company with the largest local operation, and then two of the small mom-and-pop operations. I would occasionally get attidtude from a ER staffer that I "wasn't a real EMT" Almost all of the Philly Fire Department medics were cool... and I'd be willing to lend a hand if they needed help and I was around. Most times, if one of our rigs stopped at an accident (before FD showed up)... the FIREFIGHTERS would give them a hard time... but the Medics loved it... one less chart to write.
And I've been a volunteer 911 EMT since I started class... never stopped.
Anyway... those that "look down" on you are probably not really into EMS anyway. Of course, we also need to look at our own ranks. How many people at your private "taxi service" would you actually trust to know what they are doing, and how many haven't seen a BVM used since EMT class 2 years ago?
Oh... and I work for yet another company these days... and I work about 2 transport shifts a YEAR.