Cash holdings still have risk for large amounts of capital. For example, if you had 1,000,000 in cash at a bank, it's only guaranteed up to 250,000. The other 750,000 is as risky as the institution. Compare this to a US treasury, which is substantially safer than any individual institution.

Banks can and do fail, particularly during crisis... and during a crisis safe bonds (e.g. US Treasuries) will gain in value.

I think there are a lot of people (like myself) that think it's only a matter of time before another major crisis... and are waiting to buy stocks at a steep discount.