Each dealer is different and honestly the way that they handle each person and situation can vary quite a bit. I had an old Ford serviced once and they wouldn't give me a free loaner for 2 reasons... my age (at the time) and they didnt give free loaners for service customers. When I came to pick up my car they "couldnt find the keys". I walked over and I could see them locked in my car. I didn't have a spare set with me, it was more complicated by the fact that the ignition and door keys were different, and the guy they trusted to open the door up wasn't there... which was ridiculous and I told them so. They were closed the next day, and I wasn't free on Monday, so I made a big stink and they gave me a demo car to drive for free and didnt even bother to check my insurance.
When I bought my new Malibu I asked for the windows to be tinted, and I wasn't able to wait or come back for a few days to pick it up so they gave me a loaner for free, but it was all by the book this time and I am almost 30 now.
I've also had service done where they flat out refuse and some where you can pay for it. Your age may make a difference, but it depends how they do it. If not most dealers will offer you a free ride to wherever you need to be and to pick you up again if it's within business hours and a reasonable difference. Some have a specific shuttle for this, but most will get the lot attendant to take out the keys to a new car and drive you back & forth.