Explanation there is that she's not corporeal for 100 years, she's pretty much in stasis along with Ganon's physical form for 100 years. I thought that was explained all in all, since she's effectively nothing more than a beacon of light until you actually free her from within Ganon's corrupted essence. There is no Zelda just as there is no "Ganondorf" in physical form until you make it to Hyrule and Zelda's power fails to contain the beast any longer.
Also the other explanation would be that the end of the game would have been utterly depressing if you win but then Zelda proceeds to rapidly age and die (or just SS Impa's herself into fading into fireflies), because not only would there be nothing left of Hyrule, there'd be nothing left of Link's attempt to rescue Zelda. He'd have walked away from "victory" with basically nothing but a bunch of dead friends, not even MM was that sober in its conclusion.
Sure he saves Hyrule, but he's not really of much personal value to anyone in the world any more. He's a hero that saves everyone but, then, after he does so everyone pretty much moves on with their day to day lives anyway. Barring having made friends with Sidon and Riju, he's basically got nothing else. Zelda being alive at least gives him some attachment to Hyrule, and his quest gets to continue in now working with Zelda to rebuild what was lost.