Because pay-to-view would be spun as cutting edge future of TV, while DTV is bottom of the barrel content.
But it won't be, that's the point. When the studio can keep repackaging its back catalogue without spending a cent, why would it bother being inventive in financing new projects? I time-shifted Nemesis last night (it was only the 15th time the film has screened on .au pay TV this year). Can anyone else remember which film proved the franchise was dead when it crushed ST:N in the box office? Haven't seen that one on TV in years....
If the Star Trek producers had had a quarter of the nous that the Stargate team had, we would have had several made-for-dvd titles, a mini-series or two, probably a whole slew of webisodes as well - instead we got years of nothing ending in a poor to middling, borderline offensive reboot. I paid to see that one to see Nimoy (& Pegg). I won't make that mistake again
For the record, i'm a regular supporter of crowd-sourced financing. Can't see the networks experimenting with that, either - though if anyone pitches a DS9-based fan film, let me know