Because outside the US(and to a much lesser degree the UK), xbox might as well not exist.
In the USA X1 is almost competing with PS4 and Switch, but for example sales in Japan for Switch have been 3.5M for switch(so more than 50% of X1 WW sales) vs X1 with 15000(around 0.25% of WW X1 sales).
Xbox has always had an incredible problem selling HW outside the anglosphere, so the only way they ever looked like they were competing was by dominating the US market(360 outsold PS3 2/1 in USA), which by nature of having most Gaming forums and news outlets made it look like XB was a global brand.
It didn't.
360: ~43.2M
PS3: ~26.8M
But yes, X360 really dominated PS3