Simply because it doesn't actually solve the problem, all it does is push it to one side. Let's say we sign Beto on Tuesday, he comes in, we know he can play in the first team (unlike Chermiti who is likely to come off the bench at first) and everyone is a bit happier as we go into the game next against Villa thinking we might actually have half a chance rather than worrying about how many chances Maupey is going to fluff (although I think once he gets one, he will get a load)
Now all of that might get us through the next few games and maybe even a bit more but at the end of the day we would still have a crocked player sitting in the background who we can't sell because nobody will buy because of his fitness and because of the fact it's been going on for nearly 3 years we won't get any kind of value for him (he is entering his prime anatomical years now for sport) and his record is nothing out of the ordinary (albeit things might have been different had he had better fitness) I feel sorry for Dom and the club, it's an awkward situation it truly is.