You see nothing but brooders such as the one you've shown us because most people don't know any better, and since "most people" do it, it must be terrific, huh?
I had already raised two batches of chicks in a conventional "box on the floor" and I was at a loss as to why my chicks were running, screeching away from my hands every time I wanted to pick them up. Everyday it became worse.
I had just joined BYC at the time, and I stumbled onto a thread where everyone was talking about their chicks running away afraid. A lightbulb went on in my head, and I thought, could it be that we're all thrusting our hands down into a box of chicks like we were predators of some sort?
And that was it! I made another trip out to the stores, and checked the dumpsters out back of a rent-to-own appliance store and dragged home a couple large cardboard boxes.
I had a lot of fun cutting windows and doors into it, the windows I covered in see-through plastic, and the door on the side, I left cardboard at the bottom to act as a hinge. I fastened it at the top with a popsicle stick screwed into the side.
Then I installed my new babies. What a transformation! They were calm, friendly and tame and trusting. They could see I was me and not a scary predator attached to some scary hands. After that, I always placed my cardboard brooders on a table and accessed them from the side. I have the tamest flock of chickens in the entire state, I'd wager.
I line the bottom with heavy plastic, and I plan on using puppy pads during the first few days in May when I get more new chicks. It holds up better than paper towels and they can't eat it, like they do paper towels. I always folded up my brooder boxes and reused them the next time I got chicks, but they're cheap enough you can toss them when you're done.
I got a double batch of chicks some years back, and I just went out and got another box, taped it onto the old one, cut a pass-through into the common wall, and instantly had a two-room chick condo! I cut holes near the top and slipped a stick through and hung the water bottle from it so there were no more spills and no wood shavings in the water from then on.
The thing I like best, besides tame chicks, about side-access brooders, is I can sit in a chair and play with the chicks or clean the brooder without it killing my back.
So, your choice. Stick with what "everybody" does, or do it right!