As far as I can tell, the non-screw-top caps on premium beers are simply pretentiousness.
Screw top caps don't make much change to the bottle's look (cap on or off), and don't -- as far as I know -- have any impact on the beer's quality. They can't be more expensive for companies to use, either, as you find them on all the cheaper beers.
Non-screw-top caps seem to be there to convey an air of class. There's nothing wrong with that goal, per se. But I think it's a shallow attempt at class, to forego an alternative with real benefits just to use an older-style of cap mechanism with no real distinguishing features aside from its inconvenience.
Related to this, in Mind the Gap, Paul Graham writes:
Now, thanks to technology, the rich live more like the average person.
Cars are a good example of why. It's possible to buy expensive, handmade cars that cost hundreds of thousands of dollars. But there is not much point. Companies make more money by building a large number of ordinary cars than a small number of expensive ones. So a company making a mass-produced car can afford to spend a lot more on its design. If you buy a custom-made car, something will always be breaking. The only point of buying one now is to advertise that you can.
Or consider watches. Fifty years ago, by spending a lot of money on a watch you could get better performance. When watches had mechanical movements, expensive watches kept better time. Not any more. Since the invention of the quartz movement, an ordinary Timex is more accurate than a Patek Philippe costing hundreds of thousands of dollars.  Indeed, as with expensive cars, if you're determined to spend a lot of money on a watch, you have to put up with some inconvenience to do it: as well as keeping worse time, mechanical watches have to be wound.
The same pattern has played out in industry after industry. If there is enough demand for something, technology will make it cheap enough to sell in large volumes, and the mass-produced versions will be, if not better, at least more convenient.