If you want to study Mars, actually being there opens up new avenues of study. If you're going to study Mars from Earth, it doesn't make sense to do it from the Nevada desert.
What do you mean by this objection? There are several projects practicing surviving in isolated conditions for precisely that purpose.[1]
Simply surviving on Earth, however isolated, is hardly helpful though. You need to simulate things like the lack of an atmosphere to teach you anything useful.
> There are several projects practicing surviving in isolated conditions for precisely that purpose.
Yes, and not a single one of them has ever sustained a mission for more than a few months (AFAIK). If we're going to colonize Mars we need to be able to sustain these kinds of efforts for years.
We're trying to run a marathon before we've even learned how to crawl.
