The unbroken Beale ciphers, likely enciphered using a book cipher, will remain nearly impossible to break until we figure out what key text was used to encipher them. Despite this, cryptanalysts have been trying to decipher the messages using various key texts, essentially guessing and checking in the hopes that they stumble upon the correct one. At this point, a reasonable guess is that the key text was a letter written by Beale himself, and without that letter, the ciphers will remain unbroken.
Nevertheless, people continue to try to break the ciphers with various different methods. Some test new key texts and hope to crack the cipher by pure luck; others try cracking the cipher in new ways in hopes that the messages were encoded with something other than a book cipher. Either way, these efforts require large amounts of time and creativity for even a minuscule chance of cracking either one of the ciphers.
The people who try to break these ciphers today are likely aware that they are nearly impossible to crack, and their motivation is probably not the wealth; there are many other ways to get wealthy if you are willing to put in that much time and effort. Rather, the reward they chase after is an intellectual one; they are hoping that, even by pure chance, in cracking the Beale cipher, they will be the first one to read his note, knowing that the knowledge it contains is entirely theirs until they decide to share it with the world. Even though the contents of the note are probably all related to the buried treasure which is of secondary importance, there is a unique appeal to being the first one to break a supposedly unbreakable cipher. The opportunity to become known as the person who did the impossible is tantalizing, and apparently to some, that satisfaction is worth chasing after no matter how unlikely it is that you will achieve it.