I will answer that is a round about way. I have beta tested lots of things in different fields.
I have beta tested Xbox live before it was launched, I have tested Windows server, and I have tested aquarium products for different companies. I have beta tested lots of video games too. I am not talking you buy the video game early and get beta. I mean before games launch and are in development.
For example Xbox live which was a long time ago... It was my networking experience and the fact I was a gamer. They need people that were familiar with routers, networking, internet and such. Gaming experienced helps but they did not just want gamers. Gamers are ok for stress testing servers but that is it. They did not want to hold everyone's hands for things like setting up routers etc. I was partial owner of a web company and installed DSL. Also my main job is partially IT. So that is how I got picked.
Now in the reef hobby I would guess I get asked because I have been in the reef hobby 30+ years. I have a degree in mechanical engineering and I also work for a electrical engineering place in which I do some engineering and IT work.
I also know allot of people in the reef industry. I have tested everything from Salt to Web cameras for the hobby. As for a web camera for the reef hobby you can see where knowledge of IT is helpful..
Beta testing is not always fun and games. It can be allot of work sometimes.
For Xbox live I was trying to get errors and trying to recreate those errors. Take pictures or video of errors and fill out bug reports, same with most video games. Sometimes it can be allot of work especially when something does not work as intended. Filling out bug reports etc can be allot of work. You are trying to break stuff. With reef aquarium stuff you can be putting your tank at risk sometimes. With Aquarium controllers you need to have back up systems in case it does have a issue. When you start testing a product it is not always fully functional or you hit a bug that messes things up. You brick something which does happen. You are literally trying to break the thing. You can beat your head against a wall for hours trying to fix something or get something to work and you think you did something wrong and find out yea it was a bug. Sometimes it can be really frustrating.
That said for people like me who like messing with this stuff it can be allot of fun too. For me I really like tinkering with this stuff and figuring stuff out. If you do not it is not for you.
Allot of time in the end there is nothing free. Games are good only for a certain amount of time. Windows server beta only lasted a few months and would stop working. For the reef hobby some beta equipment is built rather cheaply. Like magnet are not always coated well because the units is only made to be used shortly or they are made with cheap plastic. I have been part of betas were the equipment is shipped back to them because they do not want beta equipment floating around causing issues. You are not always testing a retail version of a product. All I am saying is when you beta test something do not expect to get something for free. That is not why you do it and another good way to never get asked back.
I never go into it expecting something for free, if I do great. I go into it trying to help the company build a better product and I also get to tinker with something different. I bolded that because it is the most important thing for anyone who gets asked. I take testing product seriously.
Sometimes it cost money too. Reef equipment sent to be tested my require pumps or plumbing etc.