Tip-toeing around mechanically makes sense when one wants to be quiet.

I find walking on concrete is more comfortable when using the whole foot, so just barely tip-toeing rather than my usual heel striking. In general, it's not a good idea to walk on hard surfaces barefoot or in sandals excessively, no matter what the FiveFingers crowd might believe. I discovered plantar fasciitis the hard way [pun not intended].

> In general, it's not a good idea to walk on hard surfaces barefoot or in sandals excessively

I think cultures where going barefoot is the norm also tend to have fewer hard concrete and stone floors. We've engineered a whole alien environment for ourselves that then require augmenting our body to deal with.