Given all then dumping, bundling, vendor lock-in and shady background deals I am not sure how voluntary this often is in practice.

Also, almost any web product could have the core functionality reproduced by 3 guys in a couple of weeks.

The actual value is in the brand, siloed data, lockin, network effect, etc.

China solved that by banning most western services and building their own, and many of the results are better than the west, yet the same network effects stop those services expanding.

These are all fairly strong arguments for regulator's to step in because the market clearly is no longer working to direct the profit towards the best products.