[Spivak]

Because monopoly means "wields monopoly power and engages in anticompetitive behavior that harms consumers." Having competition or not, having large market share or not doesn't matter one bit.

One of ways of wielding monopoly power is no longer being a price taker and being able to set prices at in practice to whatever you want.

[dcgudeman]

Your definition of monopoly contains a reference to "monopoly", so I am still not sure what your definition of monopoly is. It sounds like it is something like "big company that charges a price you think is high". Why do you think you know what the "right" price is. Isn't it a good thing the company delivering the most value is capturing the most profits? They will likely continue to deliver breakthroughs with the profits they are generating. Why would you want to kneecap a company generating so much value?