It's not really that they are "unprofessional" so much as testers operate under vastly different motivations.
That depends on your definition of "Tester". I actually am a Professional Beta Tester, meaning I often get paid to test things, and not just games. In the last few years that I've been stuck working from home I've tested a wide variety of programs, games, and even some times the odd product or two for a unrelated testing institute. It is indeed true though as you say that the motivations are completely different. When I'm being paid to test a product, what that product is will determine what my motivations are. When you're being paid to hunt down bugs you have to be able to reproduce those bugs consistently and preferably find a work around. When a tester is being paid for Quality Assurance my only job goal is to find typos, graphical anomalies, glitches, test various settings and displays and display modes and other hardware configurations. When I'm tasting a particular product or game over a period of time I work under contract for that particular company for the length of that game's beta period. Some times my job as a tester is to make sure game-play mechanics work the way they are intended to and to give feedback and suggestions to improve it. Other times my job entails playing through the same part of a game or program Over, and Over, and Over, and Over again looking for the slightest glitch or slight light and shadow variations.
In all honesty, being a Beta tester is a LOT of WORK and it can get mind numbingly boring at times. It isn't about playing games or having fun. Some times though you do get lucky and get to have a little "fun" at work. Compared to what most people call "work" they just assume testing video games is a walk in the park and it's all "fun and games" which any serious tester will tell you.....It Isn't.
Compiling a progress report for a manager who's paying me is completely different then filing a bug report here on the Elemental forums. In fact most companies have a dedicated team of in house testers (though in today's economy the testers are usually company employees who do other things and are just drafted to test from time to time). Other companies out-source this work which is where people who do what I do come in.
If you're interested in getting your foot in the door as a real tester it's not as hard as you might think. There are plenty of web sites out there who help people find work testing all kinds of products ranging from Video Games, Business Applications, to even Toothpaste and Dental Floss. Two sites I recommend are BetaWatcher.com and GamesTester.com .
Once you do a couple of jobs you'll eventually be placed on a list of "Quality Testers" and companies will e-mail you or sites you have signed up on will notify you when there is a job available or you get a job offer. If you happen to already have a background in field involving computers, electronics, or gaming, then you've already got a advantage.