Well they sometimes do (e.g. fine them) but at a scale where it matters these are companies that also have leverage - if Amazon responded 'Ehhh we might stop delivering to the UK then, Brexit is already an expense, with this too ...' and then the Government is the government that lost/banned/there-is-no-good-spin Amazon.

Within the EU, (or EEA perhaps) I vaguely recall there's some restriction against penalising for things like this, as long as the other nation is also a member state. (Since viewed as a whole, 'one EU', it should be fine, I suppose.) Struggling for the right words ro search though.