Because of this sudden death BS.
My theory on the sudden death thing is that because scombs are the cheapest, they are the most likely to be bought by inexperienced keepers. An armatus or tatauaia will normally cost about $200 usd in today's market and a scomberoides will be about $50. This means that if you know enough to be willing to spend the extra money on a tat or armatus, you're likely to know the right way to take care of it.
If you don't know how to maintain perfect water or how to cater to the specialized needs of this fish, you're going to kill your payara, regardless of what species you get. Because of this, I personally feel that scombs are a victim of both their price and availability. Its fairly well known, and it is documented in the "armatus identification thread" that ALL species of payara need flawless water and some current.
In short, because they're the cheapest and most readily available, I feel that scombs are the type most likely to be killed by an inexperienced keeper. There are a whole bunch of scombs that live a long, healthy life in the hands of experienced keepers. The issue we run into is that because scombs are fairly common and not an 'elite' fish, we don't hear much about the successfully kept individuals, because there's nothing to brag about in keeping one.
I don't know. I may be wrong, but that's just my opinion on the subject. Hell, when I first got into fishkeeping, I killed a scomb by not understanding what it needed as far as care is concerned too. :/
