In the UK a market share of 40% is enough for the competition authorities to investigate a company for monopolistic practices. It's less about market share and

In the UK a market share of 40% is enough for the competition authorities to investigate a company for monopolistic practices. It's less about market share and more about if the company is using its position in one market to create an unfair advantage in another. iOS and Android are both in a position with market power in many countries.