I'm not sure how people are coming away from my OP with this.
The scenario I attempted to present was:
"Ooh this song is nice, I'll probably only hear it in this single area in the entire game, time to cut it off with the battle theme I've heard 200 times already every 20 seconds." And then you continue to do that for the rest of the game.
I like battle themes, Cold Steel's is good, it's the implementation of them is very stale and ruins other perfectly good songs I won't have as much chance to ever hear again.
Speaking of Bravely Default, the encounter slider option actually helped with this, because picking when you want to grind vs when you just want to run around in an area picking up stuff. This meant that most of the time, I'd be hearing dungeon music in its entirety.
Sure, it kinda breaks immersion in that being able to assault a final dungeon without enemies if so you wish, so it'd be something I feel is left for smaller titles and/or director's cuts/rereleases (which BD English is - it's a localization of For the Sequel, not the original BD) but as someone who has less and less free time as the years go by, it's very welcome.
Overall, though, I do feel like the whole thing is a relic of the roots of the genre. Historically, with a precedent set by DQ and FF through the early 90s, combat has always been in this self-contained space and was in fact completely separate sections of code, and it made sense for a hard change in everything from graphics to music.
Fast forward to the PSX era, and this still persists with FF7, where combat is in a different 'reality' vs field maps, with realistically proportioned characters, etc.
I think now, with the advent of hardware which is allowing for seamless transitions, which we can see adopted by everything from Tales of Zestiria to SO5 to FFXV, it's probably high time that how JRPG battle music works is re-thought again.
FFXV as an example maybe is an iffy one, considering it's more of a seamless action RPG than an un-instanced combat scenario like ToZ/SO5, and we've already got a long history of this going back to Secret of Mana, to KH and FFXII, but its position as an entry in the mainline series, like FFXII, is an important one.