I do (even as a sometime Flash developer), but unfortunately it's not always practical. There are plenty of sites, including Vimeo embeds and Vine, which cover the SWF with an HTML element - making it impossible to right-click to play the SWF. So you end up disabling click-to-play just to see the video you wanted.

I use Chrome Canary, which doesn't have flash at all, and it seems that most sites automatically switch to HTML5.

Sometimes I'll go to a site in Safari or Chrome and and the flash won't play, but then I load it up in Canary and it works. I don't understand why those same sites don't just start with html5 if they already support it anyway.

Back when I still have Flash installed, I turned off Firefox's Click-to-play because I was unable figure out how to have it on without something like a speech balloon's popping up in the upper left corner of the window every time I visit a page that wants to use Flash.

I have a low tolerance for distractions and for anything that resembles nagging.