I disagree: they have field contact, shadowstep and secret passage, which are just better.
Jaxon + tradable actually cost mana and just wastes mana to cycle cards, without putting anything on board.
If you have 14 tradable cards, you risk to just trade a card for another tradable card and so on; in the end, you will be stuck forever with tradable cards that draw other tradable cards, so the combo pieces (and jaxon) are buried in a pile of unplayable junk 