My old Lenovo X220 convertible tablet PC was dying - SSD errors everywhere (SpinRite fixed, but I could not trust the SSD any more) I could have replaced the SSD, but chunks of the plastic case were falling off, the USB 3 port had long since failed...
Plus, although I loved my pen computer, I had started using an iPad (my daughter's, although she was not using it), so my need for portable web browsing and email on a screen larger than my phablet was being better met --- while my need for a portable computer with lots of pixels that was convenient to do real work on was not being met. The 1366x768 pixels are not enough - even my iPad mini has more resolution.
Plus, my daughter uses a MacBook, since her old school insisted on Apple. I wish that she would switch to something cheaper, like Windows or Linux on a Wintel laptop - but she is happy. And I figured that I would be able to help her more if I were more familiar with the MacBook, through everyday use.
Plus, I just upgraded my wife's and my daughter's iPhones, and I switched myself from Android to iPhone. Plus the iPad I mentioned above. The big reason for this was TouchID. Fingerprints are the Next Killer App. (I suspect that this is the real reason for the jump in Apple's sales for Xmas 2014.)
So I figured: Why not be 100% Apple and buy a MacBook?
So I bought a high end MacBook Pro Retina, 2880x1800, 1TB disk.
(Actually, despite all the reasons for considering Apple above, I might have purchased a good Windows PC with a retina level display - except that at the time I could not find one with a 1TB SSD from the manufacturer. And I had just been burned by buying an aftermarket SSD from Crucial, that turned out to have major loss-of-data problems.)