My primary reason is that I have a 2008 MBP that works fine w/ an SSD and maxed out memory... but the thing weighs a ton. Now that I'm freelance & commute by bicycle I needed something that was small, light, and could fit in a bike bar bag or my satchel. I love Macs, but used, newer MacBooks on EBay are above my current budget and the specs in used machines were lackluster given what I need for my job. A fellow developer recommended getting a Lenovo Thinkpad on eBay because they're cheap-cheap-cheap and rather decent machines for what they are. I really don't like Windows 10, and the applications I need to run don't work on Linux / don't feel like dealing with VM's / my co-workers don't use open source equivalents so files get messed up.
Apple has also been kind of stagnating on the desktop / laptop hardware front now, so, while I like being in their ecosystem, even if I had the money, I'm dubious of plunking down $2K for a theft-target notebook that is going to get banged around, that may not be supported in 5 years.