Yes, it is my job to explain to them why I think HTML5 is not the ideal option to use at this time, but so far, I've managed to convince only a few, by far not everyone. And how could I? If you look at the massive support HTML5 is getting from the "big" industry players, then many see that as enough justification to go the HTML5 route. In fact, I've been told numerous times that I was hindering progress by suggesting to use HTML4.01.
Like I said, I find it's too early to use HTML5 and don't use it whenever I can, but sometimes I have to respect a client's wish unless I didn't care about paying my bills.

