Software design, programming and support is a profession just like veterinary medicine. It takes as much training and experience to become a good software engineer as it does to become a good veterinarian. In this world, people who are good in two vastly different fields are few and far between. Veterinary practice management software is not about practicing veterinary medicine, it's about running your business in the most efficient manor possible. Software engineers in the business field are trained to analyze businesses and develop the best possible software solution.
Veterinarians typically have little or no training in software design.
Computer professionals in the veterinary industry will get continuing feedback from their veterinary clients on how to improve the product. Any good vendor will listen to suggestions from their customer base and use this information to upgrade their products. A veterinarian with a software package will not likely get much feedback from software engineers on his or her software design. The veterinary and computer fields require constant education to keep up with rapidly changing developments. The really fun part of software engineering is writing a new program and seeing it go into production.