They don't

… They don't. What I learned while working for your company isn't your company's property any more. Good ideas almost always eventually spread in our industry. And I think thats a good thing for software as a whole! You can protect your data, and your code. But you can't really stop someone quitting a job at your company, working somewhere else and reimplementing a software system that worked well. It might take years to do it, but probably not decades. I honestly think this is a pretty good tradeoff. It means if you build some software, you have head start, but not an impenetrable wall. For someone to compete, it'll take a lot of time and money just to catch up with where you are today. So it'll be hard to do but possible. This leaves the door open for any incumbent to be outcompeted in the market if they stop doing good work. And thats a good thing! Competition is painful, but it pushes us to make better products for our users. Ultimately thats better for everyone.