Yup, if weather allows, all the time. If it's just because I'm stopping somewhere quick headed to/from work, then they're loose. If it's going to be for any real length of time, I crate them because they car guard. In their crates they are very comfortable, and sleep the whole time. They have overnighted in their car crates before too.
When it's nice out I also might take them to forest preserves etc and work them one at a time. If I can see the car, I will crate and leave windows down, and put up a sun shade, so that can be done in almost any temps. If I can't see the car, obviously I can't leave the windows thrown down, so that's different.
Keeva could get stolen, I guess. She barks but wouldn't bite. Blossom probably not. lol. Big bark, lots of teeth. People tend not to mess with shepherd-type dogs who act like that IME.
Keeping them in my car is honestly vital for many reasons, mostly work. I'm expanding training services and doing in home stuff for my work now, so they will very often need to be kenneled in my car and then pulled out for demos. Plus we often get our exercise in before appointments, and stuff.