They more-or-less did, in that any significant upgrades to suits or armour require Odyssey-specific materials.What puzzles me is that Fdev is treating them as separate economies and the players are required to turn a blind eye to these inconsistencies, however didn't introduce a new separate on foot currency that isn't tradable for credits. On foot missions pay out in this new currency, everyone starts from 0 with the new currency, there is no situation of a veteran player buying all the equipment needed in 1 shop
If they'd made the two currencies unconvertible I don't think it would have addressed the problems, though.
1) People would have asked why they weren't convertible. It'd just be "why can we buy Copper but not Iron for credits" mk 2.
2) The "why not just cut open a can of hand weapons" issue still applies even if the direct pricing discrepancy is slightly obfuscated.
3) It disconnects the two play types even more. That really is into "why not just make them separate games" territory, I think. (They have said that more content combining Horizons and Odyssey play is coming) For exploration it'd be particularly weird - you scan a planet and sample the life and UC pays you in credits while exobiology pays you in spacedollars.