But it's also, IMHO, not just an anti-murder hobo trend but also an anti-setting tourism one, which I believe you also allude to.
I think these two factors are likely the main ones. A base of some kind not only gives the characters some sense of home, a place that’s theirs, but also the players. Here’s a place in this fictional world that you will create and shape through play.
Very often it also gives the campaign a sense of home as well, as a place that becomes central to play. NPCs Will often connect to the PCs through the base, and events will often revolve around the base. I’ve had a couple of campaigns that have essentially become about the base, they’re so central to play that we think of the campaign being about that place and the people in it.