You can buy Krown by the gallon and fire it in yourself via air compressor.
For $150 why bother, let someone else get covered in oil.
Well it's actually $169.50. But that's besides the point. More a matter of convenience. If Sask has only 2 Krowns who is going to drive a vehicle 100 hundreds of miles to get the vehicle sprayed. Requires an appointment and then the usual wait past the appointment time. What if you have two or more vehicles? There is a reason they sell it in bulk. It's not only for cars. Sure, if all you have is typical short residential driveway then spraying Krown is not really an option. But if you've got a large property and a proper air compressor it's easy. You know the proper amount was applied. Many Krown shops go to lite on the spray to increase margins.
It's all about DIY. You've got ppl that cram 4 dirty winter tires into their vehicle twice a year, go to the garage, stand around forever and then you have those that just change them in their driveways.
Same around here, most places will do a truck for $120 cash, which is a good deal. I do have a gallon of Rust Cure 3000 and the sprayer for it, used it a few times for touch-ups, it's easy to do on my 4-post lift in the garage, but does make a mess....fine mist of oil gets everywhere. Much easier to get take it to get done. If there wasn't a place local though, a home-sprayer is a good option. Most home kits don't have the long wands either, which are important for getting inside of quarter panels, doors, etc.
For the record; I converted from Krown to Rust Check a few years ago, better product IMO, and my local shop is really good. Any oil based spray is way better than nothing though.