Apparently, reach had been in the first edition of M&M (I didn't know this was a 2nd edition). They removed it due to the rule being too complicated and wanting combat to be more cinematic. The current system allows the hero with the sword to still have a good shot at beating the guy with a spear.
The Spearman class does get a couple benefits when using a spear (Will mod adds to initiative, bonus to Defense), so it works out for them. Other classes wielding a spear use it as a normal weapon, with no extra benefits. This ends up being simpler than my suggested house rule, allowing Spearmen to kick ass with their chosen weapon while keeping a mythic flavor in the game.