The thing is, you might not even realize the glasses are getting smaller, because businesses use every trick in the book to make them look and feel the same as always. Not only do bars and restaurants swap 14-ounce glasses for 16-ounce glasses while charging you more for the beer, but those glasses are often topped off with more foam and have thicker bottoms to ensure maximum cheapassness. You're receiving less than the 16 ounces you ordered, and a good percentage of that wasn't even drinkable (unless you like drinking solid glass).
The Wall Street Journal
"The 14-ounce one is just very insecure about its height, that's all."
Is that even legal? Eh, not really, but no one cares. In 2013, Michigan legislators proposed a law to force anyone selling pints of beer to actually give you a pint of beer -- only to find out that this brand of bullshit is, technically, already forbidden by consumer protection laws. You know, the ones no one can be bothered to enforce. The same thing happened in other states, like Maine, where the governor actually vetoed an "Honest Pint" bill and called on pissed-off beer enthusiasts to simply not support the establishments that shortchange you.