I am slightly horrified by the last answer! Matt is absolutely correct by saying that a veterinary practice is a business, and so it does indeed have to run like other businesses (ie obtain clients, cover costs, pay bills and ultimately make a profit).
However what I think is a problem with these so called "vaccination" or "neutering clinics" is that they are unfairly drawing clients into the area of practice with the promise of "cheap" treatment, only then to have to escalate the price of other treatment to make the balance. Even if insured, sometimes the cost of treatment (eg the broken leg above) may be too expensive to procede and the animal may have to be put to sleep for cost reasons.
You mention about being tied down to one practice - if everyone starts to jump around more, then I am afraid the future will be grim. Indeed you will be able to get nice cheap vaccines etc, but then try to find a practice who are willing to spend money/invest on xrays, ultrasounds, ECG's, endoscopes etc will be difficult as they won't be around as vets won't be able to make a profit from this area of veterinary practice! It is the age-old addage of "Use it or loose it!"
An example near me, was that someone set up a veterinary practice just dealing with vaccinations and neutering. Although they did claim to offer the rest of the package, had made the cost of this so prohibitively high that people would not use them. As a result, my practice would frequently see very poorly animals (often in the middle of the night) who had been subject to sub-standard neutering (poor quality suture materials, technique etc) who then needed our treatment to get better. This would usually cost the client more in total, than if they had had their operation done with our practice!