You're only jarring it to keep it from drying out. If its too wet it won't smoke well either. Theres a lot of ways to dry it out. Even jarred it can still get a bit dry. I just throw half an apple inside for a day. But there's a lot of methods.
Mason jars are nice because they're an easy way to store tobacco for a couple days or a couple decades. Once you open a tin or pouch, the clock is ticking until it dries out.