Originally, people bought it as was cheaper and had a decent set of games. Now, it probably sells for the same reason. Most of my friends ended up buying the same console, just so they could play together. Many of whom got Xbox 360. I choose not to because it didn't have the exclusives i wanted and i didn't want to be forced to pay to play online (something i rarely use anyway). Also, RROD was a huge problem which swayed over to paying extra for the PS3 (i bought a PS3 slim in late 2009, Xbox 360 slim didn't exist yet), what i didn't know back then was that i liked the PS3 exclusives far better than the Xbox 360's, i just knew PS3 had more variety. I didn't even realise that Uncharted was such a great series before i got PS3. Even now, i don't regret missing out on Xbox 360 because of all the great games on PS3.
Xbox One, PS4 and Switch (+ Many Retro Consoles)
'When the people are being beaten with a stick, they are not much happier if it is called the people's stick'- Mikhail Bakunin
Prediction: Switch will sell better than Wii U Lifetime Sales by Jan 1st 2018