I've always taken the -punk as meaning more of a style thing. Steamtech or steam-mech still work, but, when I hear '-punk', I think I automatically start thinking of a bare minimum, scraping-by type setting.
For me, that reason is because of all the cyberpunk games. To me, cyberpunk is a world where they have VERY high tech (the cyber part), but any of it that might have fallen into the players' hands is outdated, banged-up, 'fell off a truck', bought with favors for a favor from a friend of a friend.
To me, when I think steampunk, it's the same way more or less. Fantastic devices powered by steam/magical energy/ghost rock/you name it (the 'steam' of the setting), that any of it in PCs hands is second-hand or obscure prototypes.
I'm rambling, and it's early.

I guess another example of the 'punk' part of a setting would be Rebel Alliance tech in the Star Wars movies; the Empire (NPCS and the BBEG) have all the high tech, the Rebellion gets things that are older (X-wings looking generationally behind any other ship), cantankerous to upgrade (the speeders on Hoth), or are stolen tech they managed to finagle (the Shuttle Tydirium).
And yes, I generally agree the term -punk was foisted off on the public. It's the same way a movie can't seem to be made, or a book published, without going into at least one meeting saying, 'It's like X and Y and Z all together!'
Back to sleep for me.