I don't think it's really a question of ethics, but it's poor business practice. I understand not wanting to have to get the patient to pay and being the "bad guy" over money, but it is what it is.
1. If the patient has a deductible, they should know it and pay at time of service (so doctor gets his money, or a portion of it, right then, that's good). With deductibles going up every day (mine just went from $3500 to $4100 and I had NO choice in the matter) the doctor is going to have to address his collection policy soon.
2. If he waits until their deductible is met elsewhere it may be a LONG time before he gets anything (unless he knows there's an MRI or surgery in the very near future that will eat up the deductible). The doctor needs cash flow! Why not collect as soon as possible?
3. and most important! Insurance companies have a time limit to file claims, some are only 30 days! The doctor could get shut out completely! You do not get paid on untimely claims, and you usually can't collect it from the patient when it was your fault the claim wasn't filed timely.
Hope that helps!