It matters. The whole basis upon which the JS program has been sold is safety. How can a JS'er be a resource if the crew has no idea they're back there. Secondly it's a PIC perrogative, and he can't make that judgement if he never sees a soul. There's been a few illegal jumpseaters lately, you want them on your airplane? Lastly, a little respect; If I pick up a hitchhiker I darn well expect a little interaction and a personal thank you, even if it would have morally wrong to deny them a ride. (due to wx, heat whatever). Just because a "welcome aboard" can be expected should in no way cheapen the process.
What I can't figure out is why so many FAs are so bad at jumpseating. There is no workgroup in the world with a more upclose, day-to-day view of how the etiquette goes. Then they try it themselves and act like total clods. It befuddles me. Even when we are so fortunate to be acknowledged by the offline FA, usually it's a "I'm in the back." Well let it be written, let it be done, Moses. Or "I guess I have to show you this" in the valley girl accent, doing the badge thrust without bothering to remove it from the lanyard.
Then when ya call 'em on not dropping by the cockpit there's always a fascinating excuse: "I forgot," "What do you mean stop by?" "I had a long day," and my presonal favorite "you looked busy." Never in the history of airline aviation has a working flight attendant looked in the cockpit during the preflight phase and thought "they're too busy to....adjust the temperature, call for catering, call for cleaners, readjust the temperature, run for a gate check tag, run for a burger, yell at the agent, work a seat dupe, check on a dog, etc, etc" Middle of a brief, middle of a checklist, no FA has ever been stopped by such trivial obstacles. Yet suddenly as a jumpseater they become as demure as a young fawn, the cockpit is a busy and frantic place, and we certainly wouldn't want to interrupt such important goings on. W. T. F. The whole point of the preflight phase is the gathering and concentration of information peratining to the flight, of which Additional Crew Members (fascinating term) are a key part.
Paint By Numbers: "Hi I'm Suzie with AirCal and I'm looking for a ride home" Extend hand, prepare for handshake. Repeat as necessary until you find the captain, then repeat once more. Present Identification. Captain will say "Suzie Welcome Aboard!" Respond with "Oh, thank you guys so much" and this and future rides will be assured. Is it really like pulling teeth? Does it kill you to ask in a respectful fashion? Surely not. The preceding approach is guaranteed not to piss anybody off, and didn't even require a bribe.
Disclaimer: I have nothing against FAs, I like them very much, but this is my pet peeve. Obviously.