The reason for why arcade emulation is not considered a big problem is that they are not losing any profit, on the contrary the chanses of them, a very wide range of people, making money on products they produced long ago increases everytime someone downloads an old game and goes nostalgic, hey I uses to play this when I was ye high. Later on they decide to buy a used arcade cabinet for retro moments at home, do you remeber when we used to go down to the mall and play until our fingers became numb.
When they introduced consoles to the market they also introduced the concept of separating software from hardware, one set of hardware is no longer only capable of running one or two games. And since console vendors make their profit on software, they sell the rights to produce games for their system to other developers, of course they are going to complain and take drastic actions against anyone who eventually could make the profit smaller, less profit, less salory, less salory, smaller house, ugly wife and a Volvo instead of a BMW or a Mercedes.
If all emulators required a cartridge / disk / cd drive or similar, something to connect the original media to the emulator they would be less interested in hunting down people responsible for possible setbacks in their cash flow, with the Bleem situation being the exception that confirms the rule. If they had not gone they Dreamcast way chanses are that they would never have been sued and later on closed down, it comes down to pride and marketing. This piece of software allows you to play your old, not visually impressive Playstation games on another set of hardware, with enhanced graphics. From their perspective consumers are reciving a message that could and will hurt buisness and it is a direct punch to their pride. Others have achived what they could not, considering the fact that the Japaneese are are proud people nothing will stop them from losing face.
As long as emulators are not competing with the actual product I guess console vendors should be pleased, chanses are that the SNES still is generating millions of dollars over in Japan. But emulators, mainly Snes9x and Zsnes, does not compete against the console on the prime of it's lifespan. If a Playstation 2, GameCube or Xbox emulator were to be released today offering the same capabilities, the authors would probaly be sued beyond recogniction. And it would serously hurt buisness, it would force them to increase prices to make ends meet, but this would only futher piracy, which is a non feasible long term development.
And most people who are into emulation are in it for the games, they can use others tecnical achivements to play games for free, games that otherwise would set them back a couple of dollars. A fair view of my own personal interest in emulation would probaly be 60 % games and 40 % pleasure of seing what other people can accomplish. If you claim that you are only in it for the tecnology why would you then play games? Most people on this forum, except for the authors, use emulators for one purpose - to play games for free. I am sure that there are some honest people that actually own the games for the original system and are using emulators to go beyond the limits of the consoles. Most emulators offer a broad range of possibilities, easier cheating, enhanced graphics, the ability to save and load in games that do not offer this naturally.
And yes, it seems like if it's a fair assumption to assume that most rom request come from adolesents.