We know what these are. They're those annoying bits of plastic that sit on the front of your lens when it's not in use. But do you need them?
I personally never use them. They're so fiddly and awkward to get on and off, especially if you're wearing gloves or only have one hand free. The only time they get used is if I don't have a lens hood.
I prefer to keep my lens hood on and the cap home. That way I can miss far less shots. The physical size of the hood should keep things from touching the front element and give you a 'lens stand' for faster lens changes.
Leaving lens caps off gives you a few seconds extra time, and when those few seconds means getting the shot or not, I'd rather get the shot.