Because PBS offers naturally what no one else could ever guarantee even if they tried - a long life. Most shows on PBS don't produce too many episodes per season, but they all last many, many seasons. "Reading Rainbow" has been on for 15 years. "Sesame Street" has been on for 30. And "Barney" has been on for about a decade now. I would rather produce eight episodes a season and have the show last eight seasons instead of mass-producing and punching out some 22, 24, 26 or 28 episodes each year on Network Television or Syndication, only to have the show end up lasting just one or two years at most, which will be what will happen. Remember, on Network Television, it takes a mega-hit show like "ER" to last seven years, but on PBS, ALL the shows last seven years.
NO INTERFERRENCE BY NETWORK EXECUTIVES:
Because In 1978 ABC Network Executives forced Battlestar Galactica Producers to do rip-offs of Movies, such as "Shane in Space", and "Towering Inferno in Space", which lead them to producing "Fire in Space", in which the entire episode was spent trying to put out a fire in the Shuttllebay after a Cylon attack. In 1993 Warner Brothers forced the Producers of Babylon 5 to put one of their advertiser's Motorcycles on the show (product placement). In 1993 NBC Network Executives forced the producers of SeaQuest to rush into production a "Western" themed episode to air back-to-back with a Bonanza Next Generation Movie. NBC advertised it as "Bonanza Sunday". The episode was so rushed, that there were special effects errors, the ending credits weren't in the same format as the others and the episode ran short, causing the ending credits to run 45 seconds longer than usual, plus the episode was loaded with way many more "We will return to SeaQuest" segments during the commercials to pad it out further. In 1995 FOX Network Executives forced the producers of Sliders to also rip-off movies for its corporate-corrupted third season, such as "Twister", which lead to the "Twister World" episode among others. In 1999 UPN Network Executives forced the Producers of Star Trek: Voyager to place a UPN WWF Smackdown Wrestler in a cameo appearance to get cross promotion, trying to lure in the young Wrestling audience that Voyager didn't have (because it sucked). So the producers created an entire episode about a fighting match, just so they could have WWF Wrestler "The Rock" wrestle a Borg! Locutus is rolling over in his grave.
It's safe to say that PBS Network Executives aren't going to start insisting we put WWF Smackdown Wrestlers in our episodes, start ripping off movies, or start demanding product placement of Mobil products.
Find out more examples of Network Interferrence here.
ACTUALLY AIRED LIKE A NORMAL SHOW:
Because PBS won't take the show and pre-empt it, delay it, air the episodes out of order, bounce it around the schedule, and cancel it blaming you (the viewers) for not watching. Of the second season of SeaQuest of 22 episodes, NBC pre-empted 18 of them. Of 13 episodes of Strange World, ABC never aired 10.
Find out more examples of things PBS wouldn't do here.
Because Hollywood wouldn't let me do my show, even if I did waste all those years writing "Spec Scripts", starting out as an Intern, working my way up from Warner Brother's Mail Room?!?! My show has the capabilities of being done NOW. There is no reason to waste your time running through Brad Gray's Hamster Wheel to achieve your dreams. Hollywood isn't that important.