In-room, you get free internet access, but in the windowless ballroom with spotty cell-service, there's nothing available for free.
"Follow the money"
From my point of view, free WiFi became normal when it became less important because of affordable mobile internet.
From the point of view of the hotels it was about recovering their missing income after customers got mobile phones and stopped paying half a dollar per minute for using the hotel phones. There was a period when both mobile roaming and hotel WiFi was expensive, so I often went out from my hotel room and bough a local SIM-card to get internet access.
What annoys me most, is that only when I finally could get a laptop that would work a full transatlantic flight on one charge, then suddenly airplanes all got power outlets.
For extra fun, consider how phone bills attempt to "pass through" their own tax obligations, which have little to do with your own incremental usage, in the form of 'recovery fees' tacked onto bills. I suspect we'll eventually see those creep into all kinds of transactions, especially among other monopolistic/oligopoly businesses where you have little if any choice.
That's basic price elasticity of demand and entirely unsurprising. When something costs 10% more, people buy less of it in general.
We also buy more things priced at $99.99 than at $100.00, which is more of the psychological trick than it is rational price elasticity.
Hard to advertise to a wide audience when the final price after tax is one of 12 different prices depending on where they live.
I don't know of any US businesses other than waffle house that always include all taxes in the listed price, however.
Regardless, I'm not sure why people consider it such a big deal. It's consistent across the board and it's relatively basic math to estimate what the total would be.
I've lived in places that do it both ways and it's a non-issue.
I think the norm is to show whatever price you want, with some countries banning that for fairly obvious reasons.
There's still some stragglers though, offering "basic" access free but charging for higher data limits, faster bandwidth, more devices. You can often get the higher plan just by signing up for the hotel's loyalty program.
I just switched to my cell phone data if the wifi was too slow.