Because they assume that's what everyone wants, or is the biggest way to break into the WoW market. I'll continue to wait for an enhanced EQ1 that I'll never probably get. I mean fluid factions, alcohol tolerance skills, languages, dark game play that required torches/spells, killable npcs, harsh learning curves, actual exploration I.el ridable boats, ect in vanilla. There was so much depth in that game that has gone to the wayside for streamlined superficial worlds. That's how a ESO feels. Such a waste.
But really grouping is one of the main reasons to play an MMO. The interaction adds depth to the other pcs, instead of just seeing 100 other people going through the same solo on rails content.