"Doctor" is always respected, senior or not, in every society going back to the stone age. It's the nature of the profession. And doctors have authority over people in the workplace - nurses and technicians primarily - even if they don't fire or give out raises.

"Senior lawyer" isn't a thing AFAIK. Law firm partners or senior partners have management roles, or at least, influence, in their firms. Otherwise you're an associate, or in private practice, working for the government, or as corporate counsel (where again, you might manage teams of people). A random lawyer with a small private practice isn't going to command a ton of respect in society generally, even if they do very well financially.

"Senior lawyers" exist—they become judges :)

Err...ok, but again, a judge commands respect because that's a position of authority. They can order people or organizations to do things, take away their property, freedom or even their life. They can literally write the law in some cases.