When you consider that Wolf Racing started out with Harvey Postlethwaite, Patrick Head, Ross Brawn and Adrian Newey among their ranks then I think it's very worth it to have more teams in F1 if only to grow the future of the sport. For every dismal failure such as Andrea Moda or Life there were some success stories. The Toleman team had a dismal season and a half but then picked up a few points, found Senna and for a while made a name for themselves (before getting bought by Benetton).
Lots of the teams that never quite made the break through in the 80's were pretty decent at lower formula so that at the time there was little reason to suppose they wouldn't move on up. Let's not forget that Jordan were a pretty good F3000 team before stepping up into F1 with the fantastic Jordan 191 at the same time that established teams such as Lotus and Brabham could only just scrape on to the back of the grid.
There are several reasons why it won't happen though, firstly there is the fear by the teams ranked 10 to 6th at the moment that they will be eclipsed, loose sponsors, money etc and become also rans themselves. They receive a great deal of protection by the current closed shop attitude.
The second being, there just isn't the will out there for it. Most of the teams that applied in the first round of expansions under Max stood little or no chance of ever making it to the grid in the first place (just look at USF1). Until a situation exists such as that in the 70's when you could strap a DFV on the back and go racing for half a million quid (Wolf's total spend in their first season) (in 70's prices) then there isn't a huge list of people waiting to come.
It's a shame though because I agree that more cars on track makes for a better looking GP weekend.