Tours are massively expensive for underground bands and you have to think twice about every extra item you take with you.
Since the dawn of the of the touring electric musician, we've always had to lug an amp around so I don't understand why you're treating amps as an "extra". Furthermore a PA/monitor system capable of giving whats needed to preform amp-less is more expensive than any tour an underground band is gonna book. Said PA/monitor systems take up a lot of space in the van you are speaking of as well. So whats your point again?