I don't think the 'The Ancients' really cared if they lasted 100 years or 10000 years. They used concrete, or stone, or wood, based on basically the same factors we do: ease of procurement, cost, suitability, and so on.

Anyway, just because some stone tablets are still around, doesn't make it a good storage medium. Most of them are destroyed or lost. Even the ones that are still around, don't give you the perfect fidelity you get with digital storage. And of course, once it's gone - smashed into bits or lost at the bottom of the sea - it's gone. Meanwhile I can copy data stored on a digital medium as many times as I like, with virtually no loss in fidelity or transcription errors, and store those copies anywhere.

Someone else mentioned that archeology of the future will likely consist of a Google search or something like it. I suspect they're right.