i think the era of the big band is over, and we are seeing the tail end of it... U2, Metallica, all those massive bands who built themselves over years of touring and heavy MTV and radio play are coming to an end.
there will always be a handful of massively popular music acts (ie, the Taylor Swifts, Kanyes, Rihannas, Jason Aldeans, etc) and then there are the ones that suddenly rise and then in a few years from now will be residing in the 'where are they now file' (hello, 21 Pilots). with the possible exception of country music i don't see a lot of those w/ any sort of lasting power... sure maybe they'll have a few hit songs but not for a decade or longer. those days are over.
so, what's my point? good question! at the starting level, all music acts need publicity and photos are part and parcel to that. and with revenue streams via music sales getting worse and worse, the money to get a band out on the road means that the band members, their lawyer/manager, booking agent, guitar tech, sound guy and merch person are the absolute necessities. hiring a tour photographer isn't at that same level. which is why bands and their managers/publicists love to crowd-source stuff for instagram/facebook/etc. it's free, why wouldn't they!
so while i do agree that the bigger the band, the less they need generic press covering it (and really, if they are interested in selling tickets, previewing the show is way more important than coverage of a past event), it's not really gonna apply to a lot of bands (or at least the main percentage of the ones i am interested in covering).
i am not in a position to tour w/ a band as i've got a day job that i need to cover my mortgage and family expenses, etc. but maybe at some day! in the meantime, i'm happy w/ covering bands who blow through town, or the occasional trip to a festival somewhere.