Camping is common because it is the only thing a killer can do that is fully within their control
Survivors can hide to avoid being found
The killer starts chases but most can only end them by capitalizing on survivor mistakes
Regressing gens takes too long to be meaningful
Hex placement is beyond their control
Anything other than an m1 has to be telegraphed, anything that breaks this trend WILL inevitably be nerfed
Camping doesn't win games unless you are facing a very bad group of survivors, but is one of the only non-reactive actions a killer can take, one of the only ways they can dictate how the game is played.
If killer control of the game continues to be lost, no matter how "viable" or "powerful" killer is your going to see more and more killers either camp or quit.