I'll admit that I would resist asking for fear of looking like a cheapskate. How bad's it gonna be? As an adult, I've never let the price of a drink stop me from ordering one, but it might limit the number I order or cause me to make a switch after the first $25 scotch.
A couple weeks ago in Naples, I was handed a menu in English with no prices. When the waiter asked what I'd like, I said I'd like to know the prices. He apologized and handed me a menu in Italian with prices on everything. I did not feel embarrassed because I felt like the bill could have been significant if I wasn't careful.
Not all restaurants, chain or independent, operate this way (no posted drink prices). If you feel strongly about it, only frequent those who meet your requirements or whose bar menu you become familiar with. I guess if there are comment cards, you could make a suggestion as well or make the point with the server or bartender. Sometimes your feedback makes it to management or ownership and a change takes place. Please don't ask your congressman to pass a law. He's likely to do it.
In answer to your question why do many US restaurants not post drink prices, the reason is the same as why the dog licks his b****.