I ask for it.
I travel to 99% of jobs. I pack up my truck, bring a chair, a folding table, and my entire kit. It takes time and gas to come to someone for a job.
I do not charge a on location fee for photoshoots, but I do for most other jobs. (weddings, etc etc)
I ask anywhere between 10 and 20 dollars depending on how far I have to go.
I also give grads the option to come to my house, and I charge them 10 dollars less.