Even if it is capable of being a daily driver, I recently saw numbers here in Norway* showing that more than 75% of Tesla owners also own and regularly drive one or more gas (or diesel) cars. I believe the inability to tow stuff, and the limited luggage space (which won't improve too much with the Model X either), are both important reasons why people keep their Volvo V70's etc. around.

* (second only to the US in total Tesla sales, highest per-capita sales in the world)