That lack of protection would have just fueled the piracy of SACDs. People are already pirating DVD-A discs.
Probably a skewed opinion on my part, but I prefer high fidelity in an in home setting so the fact that both require special players isn't a problem with me. And both high resolution formats weren't intended for the portable audience (or even the niche headphone market), they were targeted towards users with hifi two channel or surround systems.
I do 90% of my listening on the go. I'm writing this post pent up in a hotel room 5 states away from my home. Heck I haven't seen my home in 3 weeks. So obviously portability is very important to me. Although I'm an extreme case I think the makers of SACD should have taken people who really don't have time for at home critical listening into mind.
So they'd rather let thier format die than to open it up and deal with the pirates... who already pirate that content from redbook anyway.