Essentially the jet packs reward taking the initiative. If you move to the appropriate range (say 30 cm vs rough riders and so on) they can't get you. Indeed they would have to move up then assault before the jet packs move somewhere else.
Also the packs mean you have some measure of defence against air assaulters, here moving back into the range of flak assets, positions requiring more difficult manoeuvring and/or supporting fire.
Yes you can get them - hell they are only really a problem for enemies that lack overwhelming firepower - the question is do they tie up more points than they cost and cause assaulters disproportionate damage. If so they go beyond the realm of careful use/rewarding tactics to an unbalancing factor.
Note I don't bother win them beyond getting the SC, I prefer tanks

But I guess I’ll try them at some point!
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