The point of going to Mars is to use its resources on the ground. Otherwise one could just stay in empty space, building a space station. An automated fuel factory (extracting CO2 from the atmosphere) will have to land on Mars well before the crew. And with it a power plant. And most practically the ascent vehicle which its purpose is to fuel.
So there doesn't remain much to put in a waiting orbit. Maybe the habitat, but if it and the crewed spaceship doesn't land near the ascent vehicle, they have a serious problem. Orbiting Mars doesn't give you many options anyway, until a lot of infrastructure has been constructed there. It is safer to make sure that all preplaced assets are on site and working before even launching the crew from Earth. The landers and ascent vehicles should be minimized, like elevators. A return-to-Earth spaceship, or even a Mars cycler, might be a very good idea for the ascent vehicle to dock with in near Martian space.
I'm sure someone more knowledgable here will explain how it is a huge waste of fuel to enter Mars orbit before landing, instead of just crashing down through the atmosphere on arrival.