Matt Wieters isn't the last functional catcher there will be. If the Twins scouts are able to identify a young talent in someone's system they believe can be functional for them, then that seems like a more cost effective route and quite possibly a better one in absolute terms, because we know 30+ year old catchers don't typically produce as they did in their 20s, with a few exceptions (like AJ), and very often have to be moved off the position altogether. Since the Twins already have one of those players, and he is a big fat logjam in the system, there is additional downside of having two of those types under contract. On the other hand if a cheap young catcher doesn't work out, the Twins can just outright him and move on.