Spellsword? The only "spellsword" I can find is a reference in an Epic Destiny from Arcane Power (one called "Arcane Sword," and targeted at Swordmages).
More broadly, I think the reason that there's a lot of "sword-using magic" characters is because people want different things from their melee spellcasters. Some want to use wizard spells while fighting (blade dancer), some want to use lightsabers (hexblade), some want to be mighty abjurers with blinking and fire (swordmage), some want to have more flexibility (multiclass and hybrid). It's kind of the same reason you have both Mages and Wizards, or the same reason you have 4 or 5 different ways to be a vampire. Not everyone's conception of what it should be fits a monolithic vision.