  Based on their relatively isolated environments, we argue that LBVs must be
primarily the product of binary evolution, challenging the traditional
single-star view wherein LBVs mark a brief transition between massive O stars
and Wolf-Rayet (WR) stars. If the latter were true, then LBVs should be
concentrated in young clusters and found alongside main-sequence stars with
similarly high inferred initial mass. This is decidedly not the case. Examining
locations of LBVs compared to O stars in our Galaxy and the Magellanic Clouds
reveals that LBVs systematically avoid clusters of O stars, and many reside
over 100 pc from any O star. In the LMC, LBVs are statistically much more
isolated than O-type stars, and (perhaps most surprisingly) even more isolated
than most WR stars. This makes it impossible for LBVs to be massive stars in
transition to WR stars. Instead, we propose that massive stars and supernova
(SN) subtypes are dominated by bifurcated evolutionary paths in interacting
binaries, wherein most WR stars and SNeIbc correspond to the mass donors, while
LBVs (and their lower-mass analogs like B[e] supergiants, which we show to be
even more isolated) are the mass gainers. LBVs are essentially the late
evolutionary stage of massive blue stragglers. Through binary mass transfer,
rejuvinated mass gainers get enriched, spun up, and sometimes kicked far from
their clustered birthsites by their companion's SN. This scenario agrees better
with LBVs exploding as SNeIIn and the observed isolation of SNe~IIn and SN
impostors. We argue that environmental trends of various SN subtypes are
influenced more by binarity and SN kicks, rather than tracing initial mass as
is generally assumed. Mergers or Thorne-Zykow objects might also give rise to
LBVs, but these scenarios may have a harder time explaining why LBVs avoid
clusters.
