Maybe not quite microgravity, but it's still only a third of earth's gravity. While perhaps the effects would not be quite as drastic, when you're planning to spend the rest of your LIFE on Mars that's plenty of time and a half for something similar to happen. Not to mention that the longest any single human has spent in space is only 1.25 years, there's still plenty of grey area as to what could potentially happen when one has been up there longer. Gotta test, and testing takes a while especially at this timescale. No way we get a permanent Mars settlement in our lifetimes, especially with NASA funding in the dirt. Maybe our children's.
I still think colonizing the moon first is a far more sensible option. While a mars settlement would be able to rely on local resources that the moon doesn't have, ideally whatever equipment/housing that gets sent over there should be as self-sufficient as possible anyway, and troubleshooting is a hell of a lot easier when you're only 356,700 km away as opposed to Mars's minimum approach of over 56 million km...