If anything, LAN play became less popular because it was intentionally hampered by Blizzard and other companies.
Yeah literally nobody has kids, siblings, friends. Those are all things of the past! (i'm being sarcastic)
Hell that LAN environment WAS the reason StarCraft got so hugely popular in the first place, before Blizzard got jealous and wanted to have their fingers in everything, and people still continued to play Brood War after SC2's launch.
Now, when the servers inevitably get graveyarded permanently some day, how is anybody gonna play SC2 or any of the always-online games?
> it's just that you don't want to develop, support and test features
Just let one player's machine host some of the same server code they use for their internet services?
> multiplayer via LAN is such a marginal feature nowadays
WHY?? Literally everybody has phones now, but how many local multiplayer games are there? Imagine if you could just bop your phone to your friends' and immediately start playing something together. The technology and social saturation has never been more favorable than now, but as always it's corporate greed/spying which is the biggest antifun cancer everywhere.
LANs empowered gamers with full ownership and a better ability to self organize player communities and tournaments. The always online model was heavily hamfisted by Activision Blizzard who wanted to launch their esports ambitions with SC2, seeing the KR broodwar scene as missed revenue. Look at the failed Overwatch League (OWL), Heroes of the Storm, Hearthstone and even reforges of classic RTS.
DOTA/League spawned from lan/bnet use map settings games and arguably Dota rise to success started in Lan cafes before hitting mainstream success on bnet.
I acknowledge that many likely don't ship Lan because it's being seen now of days as extra, but I think that's pointing to the consequence as the root cause what the major entities wanting control and ownership on their platforms. It didn't used to be an extra feature 0.1% used, we were pivoted into this to profit larger corps and it's not a tinfoil hat conspiracy, it's just following where the real money was and investors want to be middlemen on platforms.
There's also a complex networking situation when people are behind NATs, firewalls, etc.