system
Given the following post, respond as if you're commenting on Reddit:
human
[Doctor Who] Why does each Doctor attach themselves to a particular earth time period?

The Doctor can (and does) travel anywhere in time and space, with one notable exception. When visiting modern day earth, each Doctor only ever seems to visit a particular time period, interestingly in chronological order of their regenerations. From 1 in the 60s to 12 in 2015. 

He holds this pattern fairly rigidly as well, never crossing in to the other regenerations' territory, and only choosing companions from one time period. The war doctor didn't even know what cup-a-soup was, for instance. At the risk of answering my own question, could it be that the Doctor uses earth's timeline as a means of anchoring himself and providing a sense of linearity?
gpt
He doesn't. You may be interested in Big Finish, a Doctor Who production which makes up more of the Doctor Who lore than the TV Series itself. Featuring primarily the Fourth to Eighth Doctors, though now incorporating the Third, War, and to a lesser extent, First and Second Doctors, with small stories for the Ninth, Tenth, and Eleventh (the three of whom are all taking Winston Churchill through time and space).

Just as an example, the Fifth Doctor comes to own a house in London, however, it's the Eighth Doctor who actually ends up living there for a while during WWI.