A DSLR/video camera confines you to operating within the supervision of a guide or warden at all times (as do national park rules in most areas).
And yes there are restrictions - for the main you cant just go for a walk and wandered wherever you feel in the park with a DSLR. Regulations for safety and disturbances apply to all.
You're also incapable of scaring off wildlife 400m away by pointing a DSLR at it as opposed to flying a drone near it.
You're also not annoying everyone else in the group with a nice, quiet DSLR vs a constant buzzing drone.
The drone community has proven time and time again it isnt grown up to self police (as posts in this and the other thread show with "i want to fly stealthily/i wont get caught" and so on.
Even if someone is "held accountable" its too late -the damage is done. The wildlife is spooked, other paying customers didnt get what they wanted to see and so on. No point with that risk.
Many drone owners (including many on here) so seem to think they're the centre of the universe but in reality we're a minority group operating where the majority is at best neutral, at worst hostile and operating devices that are capable of causing annoyance to both people and animals.