Ultimately, the reason that TOs should care about doubles is that it is both competitor- and spectator-friendly. For competitors it increases game depth by adding new positions/situations and new tools/opposition. For spectators it promotes more character variety (due to a higher level of balance amongst the cast) close-range interaction more often in more match-ups (largely due to the new tools and opposition). Whether it is shielding in Brawl, modern crouch canceling in Melee, or the ubiquitous ledge camping in both games, the past two iterations of Smash clearly favor relatively defensive tactics in singles. In doubles these options are significantly weaker due to the ability of synchronized attacks to defeat any single player's possible actions (this provides another layer of real skill gap that emphasizes practice and adds a unique disadvantageous situation to game depth). In other words, the more time spent is in a 2v1 situation, the more likely that the team is going to win. This practically revolves around aggressive and rushdown play which, nearly by definition, requires more frequent action, although zoning doubles teams are possible -- albeit more difficult -- to play. This allows a wider spectrum of valid character selections, play styles, and talents when compared with singles play, while still including the skills necessary to succeed in singles play to varying degrees.