Ever go field herping? Or lose a snake in your own home? Snakes are hard to find! I go often and there are just times when you don't find anything--especially in a place as large and hard to travel in as the everglades.
I've heard varying statistics on how many there are...some people say there are tons, some people say there are very few. Until they are gone, it's really hard to say for certain.
It's hard to even give away a large, wild and angry burm. Especially since healthy CBB morph babies are getting to be so cheap. Burms are big, too. It's hard to have a collection of burms. Maybe if they were something like ball pythons that more people could successfully house dozens of, it would be easier to get them homes. I know some people out there who try their hardest to give them homes, but.. sometimes you just can't find homes.
And at least the ones who are killed go for a good purpose--to study the problem and see how bad it is. They can see if endangered or pet animals were eaten, and prove that no, a burm doesn't eat thousands and thousands of animals in a month. So it helps stop the insane amount of bad media, hopefully. Back up the truth with facts. It's sad how we have to get those facts, but if it ends up saving more of them, I think it's worth it.
I know if I was to get a wild caught animal I'd rather get it from a place where it was invasive rather than taken from their natural home. But there are only so many people who can even house a burm. If you can and want to save them, maybe you can find a way to contact people collecting them and tell them you want to save and help rehome the adults.