I have covers on my driver, my 3-wood, my 5-wood, and my 3-iron hybrid.
I don't have covers on anything else in the bag. I used to cover the putter, and I prolly still should, but I lost so many putter head covers over the years that I gave up.
If like am riding, I often leave the cover off the driver because it doesn't bang into the ither clubs.
Growing up, I always walked and always carried. I actually loved that sound of the iron heads gently bumping into each other as I walked. The sound irons make when they bang into each other while driving a cart over a big bump, on the other hand, I don't enjoy.