So what? Nobody is obliged to serve any market, or a markets obliges to open for individual companies. If company A won't, companies B and C propably will.
If by market leader you mean creating monopolies, or oligopolies, there are rules againstt that in place. So there seems to be some concensus of seeing those outcomes as non desireable. And those rules cover consumer protection and choice, Microsoft has some experience with that when it comes to Internet Explorer.
if your goal is more protectionism, then it’s great. but if you want to produce market leaders then it’s bad.