It's the pads that you don't want to oxidize, the rest doesn't matter. The oxidation creates soldering difficulty.
The pads are for the things that are supposed
to go there. Sometimes, you end up wanting to pop a few post-build holes in the board for parts that weren't in the original design, but help extract more from it, or to run wires out to toggles to make something more flexible. I'm in complete accord with your rationale of "Don't knock yourself out about things that don't really matter". I just happen to be one of those people for whom traces often represent as critical a landing spot as pads do.
And it's not just for adding parts, either. Sometimes, one of the most useful aspects of a debug is to cut a trace and isolate something. When the problem is identified and fixed, an oxidized trace is not quite as receptive to bridging that gap again with a tiny piece of resistor lead.
So, long story short, I find it helpful, for my own purposes, to make sure the whole
board is tinned. I see enough oxidized copper every day looking out at the roof of the Parliament buildings.
But I can fully understand where it is not quite AS critical for many others.