Does it? Let's take a look. Yes, it's pretty bone dry. A desert, if you will. But even Mars has polar areas covered in frozen white stuff of some sort. And the rest of the planet has hills, mountains, plains, gullies, plateaus, possibly even remnants of volcanoes from long, long ago. It has enough atmosphere to blow up some dilly dust storms. So it's got topography, and if it had enough atmosphere and water to produce a less-restricted range of weather, I'm certain there would be different flora in different areas on the planet. Keep that in mind if you are considering Terra-forming Mars.
But when I have a story set on another planet, I seldom have my characters running around in spacesuits. My reasoning is that the planets they explore first – if all other items were equal – would be the ones they could live on most comfortably, without heavy suits to protect them.
So now let's look at Earth. It is not all jungle, nor desert, nor mountains, nor swamps. It's a mix. I've lived here all my life, in various sections of one little piece of one continent, and even I can attest that the terrain and fauna is varied.
For instance, hubby and I recently drove from Omaha (Nebraska) to Reno (Nevada) for the World SF convention. I was at the tail end of a stomach flu, and don't remember much of the trip out, but I was actively looking during the trip back. What did I see?
Nevada – Not exactly the flat desert I expected; the ground was pretty well covered with arid-area plants, and was flat, but the elevation was high, and the tops of mountains stuck up through the plateau, their sides eroded into gullies.
Utah – Most of what we drove through was salt flats. The ground was utterly, utterly flat, covered in off-white salt. I didn't attempt to draw the salt factories (they were there), but in the distance, you could still see a few mountain tops poking up from the ground.
Northeast Utah – As soon as we got past Salt Lake City, we headed even higher into the Rockies. For a bit less than 100 miles, the roads were like snake paths as traffic slogged their way up sleep inclines and tried not to slide down the other side too fast. Very reminiscent of the Sunday drives my folks thought were fun when we lived in Colorado many decades ago.
Wyoming – Technically, the Rockies tromp right through Wyoming, just like they do Colorado. The elevation, for the most part, is over a mile above sea level. But in Wyoming, it seems like all the peaks are connected, so what you see above 'ground level' is really 'rolling mountain peaks', kind of like really tall rolling hills.
Nebraska – And then we hit Nebraska. Now, the Panhandle in western Nebraska still has some hills, but they peter out pretty quickly, leaving you with ... utter flat. Occasional gully, a tree now and again, and once in a while a few small hills clumped together for safety. There might be cattle in the fields, nibbling the ground cover, or the fields might hold a crop of corn or soybeans. For the most part, things are flat.
There you have it. We only traveled 1000 miles, and found a lot of different terrains, different faunas. Don't try to tell me North American is all farmland, because it's not. And if just one continent is not homogenous, how can you figure the entire planet would be? Plan your planets a little more carefully than that.