And originally pounce was a polymorph only benefit. If we ignore the obvious sources like the barbarian ACF or the lion's pounce spell/power, other sources of pounce are actually quite equitable to the benefit spring attack brings. Things like two weapon pounce, lion tribe warrior, blood spiked charger, etc. Charging is harder to pull off though. So it does require an environment tailor made for you to actually pounce more than just once every few combat encounters and it to be effective. In my experience, charging just doesn't happen often enough to warrant the single minded focus.
Then again, we could always play with the words on the page quite literally. By the rules, an attack is a standard action. It does not say an attack action is a standard action. With that we could take it that it's defining the term "attack" for use in reference to actions taken. Thus a full attack allows you to take multiple attack actions. Goes against the entire 2 decades of history we've got going on, but it would put spring attack on the power level of pounce barbarian in a way with your increased mobility, and it would make whirlwind attack much more attractive and less immobile.
That said, you're right that spring attack just doesn't get the kind of support charge does. However, I do think it's more that charge is a base action any one can make while spring attack is a feat and requires a 3 feat investment. WotC didn't really do much support for any particular feat.